SHINE 2025 Sessions and Summary Reports

Session Description

Y. Yang (University of Delaware), W. Matthaeus(University of Delaware), Lingling Zhao (University of Alabama in Huntsville)

Entropy is a central concept in classical equilibrium thermodynamics and its extension to local thermodynamic equilibrium is an essential feature in deriving Navier Stokes equations in collisional gases. The approximations leading to the Boltzmann equation are sometimes applied also to low collisionality plasmas. In that case there is a reasonable justification for use of the Boltzmann-Gibbs entropy functional “f log(f)” in space plasmas. However in the Vlasov Maxwell system where collisions are formally absent, the system is formally reversible, this raises a major issue due to the implied constancy of the “f log(f)” entropy. Another major issue is that the Boltzmann entropy does not include any contribution due to nonuniform or turbulent flows, even though physical intuition suggests that turbulent heating should increase entropy. While some might argue that heating requires collisions, another line of thought suggests that a more general formulation of entropy is required. Other ideas are available including nonuniform extensions to the entropy formulation, information (Shannon) entropy applied to the fields themselves, and nonextensive entropy. This session invites broad discussion of the above issues and merits of various novel and alternative entropy formulations. The issues raised have substantial implications for theory, simulation and observation as well, including understanding heating of the corona and solar wind associated with shocks, turbulence, and reconnection.

 What is the relevance of thermodynamic entropy in low collisionality plasmas?

What do we learn from the recently developed formulations of entropy (spatial dependence, information entropy, etc)?

Is there an extension of standard Boltzmann entropy that takes inhomogeneous flows and turbulence into account? What are we missing if we do not?

Progress and Prospects Report

Scene setting speakers: Vladimir Zhdankin (University of Wisconsin-Madison), Haoming Liang (University of Maryland and NASA GSFC)

This session focused on the relevance, formulation, and measurement of entropy in weakly collisional and collisionless space plasmas, where traditional thermodynamic definitions may break down. It began with a theoretical overview of entropy in nonequilibrium collisionless systems, highlighting concepts such as entropy cascades, the principle of maximum entropy, and the derivation of generalized velocity distributions like the kappa function. The session also addressed both simulation and observational efforts to quantify entropy in space plasmas. On the fluid side, entropy was discussed as a coarse-grained diagnostic tool for studying reconnection, turbulence, and shock processes. On the kinetic side, the use of Boltzmann-Gibbs entropy was explored to identify non-Maxwellian features and track energy conversion across scales.

Main points of discussion during the session include the following:
(1) Coarse-grained entropy and reversibility: Several participants emphasized the tension between the formal conservation of fine-grained entropy in collisionless systems and the observed irreversibility in space plasmas, suggesting that coarse-graining or phase-space mixing is essential to capturing real entropy production.
(2) Entropy diagnostics in simulations and observations: Discussions highlighted the importance of developing and validating entropy estimators suitable for use in particle-in-cell (PIC) and Vlasov codes, as well as in spacecraft data. Conservative collisional operators and high-resolution diagnostics were emphasized as necessary for accurate modeling.
(3) Instrumental limitations and measurement sensitivity: It was noted that the sensitivity of particle instruments, such as Faraday Cups, affects entropy measurements, complicating comparisons between models and observations.
(4) Non-Maxwellian distributions and generalized entropy: Considerable attention was given to kappa distributions in the solar wind. Questions arose around their origin, variability, and whether they can be derived self-consistently from entropy maximization with meaningful physical constraints.

Future prospects include:

1) Applying thermodynamic entropy concepts to fluid turbulence modeling, which can provide a macroscopic perspective on entropy evolution in magnetized turbulence;

2) Strengthening the connection between theoretical models and in situ spacecraft observations. For example, analyzing observational measurements of the kappa distribution index as a function of solar wind parameters can yield valuable insights into the variability of nonthermal particle distributions, helping to guide future efforts to bridge theory with observational data.

Session Description

Siyao Xu (University of Florida), Xiaocan Li (Los Alamos National Laboratory), Yan Yang (University of Delaware)

Turbulence, reconnection, and shocks are key mechanisms driving energy dissipation and particle acceleration across a wide range of plasma environments. While traditionally studied individually, recent observations and simulations reveal complex interactions between these processes. Understanding this interplay is crucial for uncovering the physics of energy transfer and particle energization in solar corona, solar wind, Earth’s magnetospheres, and cosmic plasmas. This session aims to establish such fundamental interaction and their mutual impact on particle energization, foster cross-disciplinary collaboration, highlight the significant progress being made and identify critical open questions to guide future research.

How do turbulence, reconnection, shock interweave with each other, such as reconnection-driven turbulence, turbulent reconnection, shock-turbulence interaction, and shock-reconnection interaction? 

How do these processes mutually contribute to particle energization? 

What is the role of turbulence in their energy dissipation and their associated acceleration mechanisms? 

Progress and Prospects Report

Scene setting speakers: Colby Haggerty, University of Hawaii; Alexandros Chasapis, Laboratory of Atmospheric and Space Physics, University of Colorado Boulder

Scientific progress:

1) The interplay between magnetic reconnection and turbulence.
New observational (e.g., MMS) and numerical evidence was reported and discussed on their interplay, including turbulence altering magnetic reconnection on multiple scales, reconnection driving turbulence (free energy in magnetic fields), and turbulent dissipation via reconnection (free energy in turbulence).

2) New perspectives on defining heating collisionless plasmas.
While no consensus was reached, the distinction between thermal heating and non-thermal particle acceleration was broadly recognized by the audience.

3) The “injection” problem in reconnection and shock acceleration.
Differences in the transitions from thermal to non-thermal particles in reconnection and shock acceleration were identified and discussed. These differences are closely tied to how “injection” is defined. While shock acceleration has a well-established injection problem, its counterpart in reconnection studies remains less clearly defined.

4) How to diagnose the detailed acceleration physics in reconnection.
The relevant physics discussed includes reconnection and associated particle acceleration mechanisms, the roles of parallel vs. perpendicular electric fields, electric potential in trapping and Fermi acceleration, guide field effects, and self-generated turbulence. Efforts to connect with turbulence studies include applying common diagnostics for energy dissipation. Observational results spanning solar flares, the heliospheric current sheet (PSP), and Earth’s magnetosheath and magnetotail (MMS) highlight strong community interest across multiple scales.

5) New perspectives on defining turbulence
Discussions highlighted new perspectives on defining turbulence in shock regions, Earth’s magnetosheath, and magnetic reconnection sites, emphasizing nonlinear, multi-scale energy transfer as a key feature. There was debate over whether traditional turbulence theories—often developed for incompressible plasmas with clear scale separation—are appropriate for characterizing turbulence in these environments.

Future prospects:

1) Future efforts should aim to clarify the relative contributions of spatially intermittent dissipation via small-scale reconnection versus more uniform turbulence–particle interactions in driving energy dissipation and particle energization in collisionless plasmas, and how these vary with plasma conditions. Understanding energy partition across species, scales, and between thermal and non-thermal populations remains a key challenge, as does resolving the differing injection processes in turbulence, shocks, and reconnection. Addressing these questions will require coordinated multi-scale observations and large-scale numerical simulations.

2) Future sessions could benefit from a more focused scope by narrowing the topics. For instance, reconnection and turbulence could be addressed in a dedicated session. The heating problem, which closely relates to Session 01 on “Entropy and its role in space plasmas,” could be merged with that session. Similarly, discussions on particle acceleration align well with Session 03 on “New insights into particle access and transport in the inner heliosphere” and may be combined accordingly.

Session Description

Robert C. Allen (Southwest Research Institute), Erika Palmerio (Predictive Science Inc.), Lengying Khoo (Princeton University)

The modern collection of interplanetary observatories allows for unprecedented study of the longitudinal and radial variation in measurements of suprathermal to energetic particles for a multitude of events. However, characteristics such as how wide-spread solar energetic particle (SEP) events are, radial variations in particle fluence and spectral profiles, as well as composition characteristics are often found to be highly variable from event to event. This motivates a robust community discussion on future investigations needed to better constrain and understand the fundamental physics governing particle access, transport, and variability within the inner heliosphere.

1) What are the dominant physical processes that govern the longitudinal extent of SEP events?
2) What fundamental drivers that establish and modify observed variations in SEP properties (e.g., spectra, composition, etc)?

Progress and Prospects Report

Scene setting speakers: Christina Cohen (CalTech) and Nicolas Wijsen (KU Leuven)

The session focused on the physical processes governing the longitudinal extent and variability of Solar Energetic Particle (SEP) events. This centered on robust discussion between theorists, modelers, and experimentalists on various avenues and pathways for particle diffusion, transport, and sourcing.

While some ordering factors for the longitudinal spread of SEPs have been found, such as the wider SEP expanse with larger shocks, many events have been highlighted that seemingly defy these correlations. These discrepancies indicate that while some underlying mechanisms may generally act on the longitudinal spread of SEP events, higher-order complexities exist that are not fully understood or appreciated. Some of the discussed potential drivers for this variability are higher-order perturbations to the CME shock geometry, roles of the heliospheric current sheet in particle transport, and coronal structures, including quasi-separatrix layers and pseudo-streamers, facilitating particle acceleration and spread. These highlight current challenges and debates within the community regarding whether SEP transport is truly diffusive, how turbulence affects particle transport, and species-dependent impacts on transport.

Motivated by the discussion in the session, future research needs to focus on several fronts. First, case studies of specific events, such as the October 2021 events, are needed to test hypotheses and potentially ‘falsify’ assumptions. Additionally, more statistical analysis is required to investigate the role of heliospheric current sheets on SEP transport, especially longitudinal transport in the inner heliosphere. The discussion also revealed several modeling enhancements that need to be considered, such as incorporating dynamic CME/SIR structures and extending magnetic field models from the corona into interplanetary space. Lastly, the discussion highlighted key observational needs, such as multi-point spacecraft datasets to resolve both radial, longitudinal, and latitudinal SEP variations.

Session Description

Nikolai Pogorelov (UAH), Federico Fraternale (UAH), and Ameneh Mousavi (Space Science Institute, Boulder, CO)

Pickup ions (PUIs) are generated in the heliosphere and in the local interstellar medium (LISM) through charge exchange, photoionization, and electron impact ionization of neutral atoms, predominantly hydrogen (H) and helium (He). In the distant solar wind regions traversed by New Horizons (NH), non-thermal PUIs dominate the internal energy of plasma, mediate the properties of collisionless shocks, and give birth to energetic neutral atoms (ENAs), some of which are detected by the Interstellar Boundary Explorer (IBEX), Cassini INCA, and SOHO HSTOF. Recent studies emphasize the need to reassess our understanding of the proton and electron velocity distribution functions, and the underlying physical processes, which is crucial for refining interpretations of the observed ENA fluxes and preparing for new IMAP observations. Additionally, PUIs play a critical role in interpreting Voyager observations in the VLISM, ultimately advancing our understanding of the unperturbed LISM properties. The properties of electrons are crucial also for descriptions of the interstellar dust entering the heliosphere.

1. What are the time-dependent properties of the (multi-component) PUI and electron velocity distribution functions and their impact on the global heliosphere?

2. What are the physical processes affecting ENA observations of the globally-distributed and ribbon fluxes, and how can theoretical and numerical ENA models be improved to better fit observational data? 

3. How to reconstruct the heliospheric magnetic field at NH and PUI properties at Voyagers?

Progress and Prospects Report

Pickup ions (PUIs) are generated both in the heliosphere and in the local interstellar medium (LISM) through charge exchange, photoionization, and electron impact ionization of neutral atoms, predominantly hydrogen (H) and helium (He). In the distant solar wind regions traversed by New Horizons (NH), non-thermal PUIs dominate the internal energy of plasma, mediate the properties of collisionless shocks, andgive birth to energetic neutral atoms (ENAs), some of which are detected by the Interstellar Boundary Explorer (IBEX), Cassini INCA, and SOHO HSTOF. Recent studies emphasize the need to reassess our understanding of the proton and electron velocity distribution functions, and the underlying physical processes, which is crucial for refining interpretations of the observed ENA fluxes and preparing for new IMAP observations. Additionally, PUIs play a critical role in interpreting Voyager observations in the Very Local ISM (VLISM). The session had two scene-setting talks given by William S. Kurth (University of Iowa) and Eric Zirnstein (Princeton University), which were followed by an extensive discussion. The attendees were provided with an extensive update on the results of the Voyager mission. In particular, recent observation from the magnetometers (MAG) and plasma wave instruments (PWS) were discussed in the context of physical processes occurring in the LISM region perturbed by the presence of the heliosphere. There was a considerable discussion concerning the current regime in which Voyager 1 resides and how it relates to the heliosphere-LISM interface. It was emphasized that the theory of plasma wave generation in the VLISM should be updated, because the current criteria seem to be highly inaccurate. Nevertheless, plasma oscillations were observed beyond the heliopause over the same range of frequencies of the radio emissions observed in 1983 and 1992. While a number of shocks and pressure fronts were identified, not all of them are associated with either enhanced turbulence level or plasma wave emission. A question was raised about the possibility of weak shocks with structure width exceeding the proton inertial length 104 times can efficiently accelerate electrons and creates beams generating plasma waves. Explanations of the observed radial gradient of the electron density have been discussed, together with the puzzling behavior of the radial component of the interstellar magnetic field. A new regime of plasma collisionality discovered by Voyagers has been discussed from both observational and theoretical perspectives.

Energetic neutral atom measurements performed by IBEX have been discussed, including different scenarios for the enhanced ribbon flux and challenges in reproducing the energy spectrum of the distributed ENA flux. The necessity of further improvements in the kinetic description of PUIs was emphasized. The session discussion especially addressed the importance of adding interstellar neutral He to theoretical models of the SW-LISM interaction. As a consequence, the models should take into account the presence of thermal and nonthermal He+ ions, and consequently He++ ions. It was acknowledged that electrons require a separate treatment. In addition, ion-ion and ion-electron collisions should not be ignored in the VLISM. Preparations to the first results of the IMAP missions were discussed. In addition, a question was raised about the possibility of using theory and in situ measurements for the derivation of magnetic field and New Horizons and PUI properties at Voyagers.

Session Description

Lulu Zhao (University of Michigan), Slava Sadykov (Georgia State University), Maher Dayeh (SWRI)

Large eruptions on the Sun have the potential to release solar energetic particles (SEP) into the heliosphere. These highly accelerated charged particles pose a radiation risk to hardware and astronauts in space. The research community regularly cites the potential for SEP events to debilitate or kill astronauts. But how realistic is this scenario? We will discuss historical SEP events measured since the start of the space age and their impacts on humans and operations, including typical and worst case scenarios.

What is radiation dose and what do all the different units mean (e.g., Gy, Sv, Gy-eq)?

What are the actual human health outcomes as a result of radiation exposure from SEP events in realistic and worst-case operational scenarios?

How might SEP events be handled during the upcoming Artemis missions?

A presentation is available that supports the topics of this session: https://helioshine.org/what-are-the-human-risks-of-solar-particle-event-radiation-exposure/

Progress and Prospects Report

The aim of this session was to better inform people about the confusing concept of radiation dose, how it is calculated, and explain the different units of dose and how they are most appropriately used when talking about the health effects. Then, using this clarified knowledge, the goal was to interpret health outcomes for astronauts during 4 examples of solar energetic particle events:

August 1972 King event: the most extreme SEP event of the space age, although the data is not fully complete

October 1989 series of events: the Space Radiation Analysis Group’s reference event for radiation protection

March 7, 2012: the most intense event of Solar Cycle 24 and a Top 10 event

May 11, 2025 Gannon “Superstorm”: most publicized event of Solar Cycle 25 with an extreme geomagnetic storm by fairly small associated SEP event

A reference presentation prepared for the public by NASA’s Space Radiation Analysis Group was available for attendees to download (link above).

In the first part of the session, the scene setters went through the different types of dose, the types of parameters needed to calculate them, how they are different, and what they are used for. The scene setters emphasized which units and methods were used explicitly for cancer risk and which were used for acute effects, like nausea or skin irritation. They described effective dose (full body dose), which is used by NASA to track astronaut career dose limits, and demonstrated that the different methods (ICRP60, ICRP26, ICRP103, NASA) used give different answers because they have different schemes to weight the underlying radiation field. There were lots of questions during the session aiming to gain clarity. Some attendees were interested in making sure that the way they taught the topic in their classes was done correctly. It also came up that the radiation field matters (e.g. galactic cosmic rays versus SEP composed mainly of protons or X-rays used in medical procedures) and that you can’t just take calculate results for one case and then use simple ratios of the numerical answers from the different methods because a different radiation field will result in a different relationship between the values. The scene setters showed the doses required to cause various acute health effects, then we launched into the SEP health outcomes for an astronaut in 5 shielding scenarios:

space suit (0.3 g/cm2) in free space
thin shielding (3 g/cm2, thin part of Gateway) in free space
thick shielding (30 g/cm2, thick part of Orion) in free space
space suit on lunar surface
thin shielding (like a lunar lander) on lunar surface

The first discussion focused on the1972 King event which did result in the most extreme outcomes in this analysis. An astronaut in a space suit for the entire duration of the multi-day, multi-SEP event would have experienced significant health effects with a small chance of death likely close to 5%. October 1989 was less extreme but could lead to acute effects if astronauts stayed in a space suit or thin shielding in free space the whole time. Astronauts behind thick shielding were always fine with zero acute health effects in all cases, although an increased long-term risk of cancer is always present with any radiation exposure.

An outcome of the discussion was that SRAG and the SEP community’s job is to be able to understand, forecast, and monitor the space radiation environment so that we know when to move astronauts from thin to thick shielding for maximum protection and to avoid acute effects in the most extreme cases. Our operational actions do protect astronauts and, in a realistic situation, they should not get close to experiencing acute health impacts. However, it is important to be aware that shielding matters and without significant shielding, there are dangers from the strongest SEP events. One attendee pointed out that an event just a few times stronger than Aug 1972 would have a high probability of lethality, so we’re not so far away. However, it should be qualified that such a slightly larger event would be guaranteed to be lethal only if the astronaut hung out in free space in only a space suit for the whole time. One attendee commented “we’re going to have to change all our presentations” after the discussion, so it was clearly acknowledged that it’s not accurate to say that SEPs will kill astronauts all the time. The scene setters emphasized that SEP events are indeed an important health risk and must be managed, be they should also be represented in a responsible way.

Session Description

Francesco Pecora (Delaware), Alex Chasapis (Colorado), Julia Stawarz (United Kingdom), W. Matthaeus (Delaware)

Space plasmas are permeated by phenomena across vastly different scales, from coronal mass ejections to kinetic effects involving individual particles. Our understanding of these phenomena depends on space missions that gather data throughout the heliosphere – from regions close to the Sun, through near-Earth space, to the heliosphere’s outer boundaries.

Different space missions are dedicated to investigating different regions of the heliosphere.
Parker Solar Probe ventures closer to the Sun than ever before, Ulysses and Solar Orbiter move outside the ecliptic plane, various probes are dedicated to different planets, and the Voyager spacecraft recently reached the interstellar medium. However, these missions rely on single-point measurements. While invaluable for discovering properties of unexplored regions, such measurements limit our understanding of space plasma dynamics.

A significant breakthrough came with the Cluster and Magnetospheric Multiscale (MMS) missions, each employing a constellation of four spacecraft for simultaneous multipoint measurements. These missions yielded extraordinary scientific returns and enabled innovative techniques like the curlometer and wave telescope through which previously inaccessible phenomena could be investigated, including wave-turbulence interactions, dissipation processes, emergence of local equilibria, and direct studies of the Vlasov equation.

We are now facing a similar leap forward with novel multipoint multiscale missions to be launched. These missions (HelioSwarm, Plasma Observatory), not only provide simultaneous multi-point measurements (at 9 and 7 points respectively) but also cover a range of multiple scales, providing the first-ever possibility to directly investigate multiscale problems in space revealing the full complexity of space plasma dynamics.

Additionally, the growing number of spacecraft, allows for non-conventional multipoint studies such as PSP-Solar Orbiter alignments, and multi-spacecraft CME studies, using L1 missions as a swarm.

What science, currently inaccessible, is going to become available with new multipoint multiscale missions?

What tools do we need to develop to enable this new science?

Can we extend these tools to existing multispacecraft missions?

Progress and Prospects Report

Scene setting speakers: Kris Klein (U. of Arizona), Maria Federica Marcucci (IAPS – INAF)

Scene setters Kris Klein (deputy PI of HelioSwarm) and Maria Federica Marcucci (PI of Plasma Observatory) presented these new multipoint, multiscale missions and the science opportunities enabled by new observations. The session motivated discussion on the development of multi-spacecraft analysis methods and highlighted the need for multi-point observations to address major science questions in heliophysics. We discussed the limitations and possible extensions of existing methods and observations. Following a prompt from Robert Allen, we discussed the development of collaborative approach to provide the community with open-source libraries for the analysis and visualization of novel more complex data sets to promote advancing our understanding of energy transfer, turbulence, and dissipation across the heliosphere, moving beyond the inherent limitations of current single-point or single-scale observations.

Progress:

Measuring multi-scale energy transfer and dissipation in turbulence:
We discussed the limitations of existing methods, focusing on multicomponent models of turbulence, validity of Reduced MHD, measurements of spectral anisotropy relevant to critical balance and helicity barrier models, and the field-particle correlator technique. Siyao Xu brought up the importance of understanding effective viscosity and determining the mean free path in a collisionless plasma.

Space-time evolution and Taylor’s hypothesis:
Single-point measurements mix spatial and temporal changes, relying on Taylor’s hypothesis. Effects of frequency shifts and spectral distortion due to violations of this hypothesis are a major concern, for example in Parker Solar Probe data at perihelia, and a modified Taylor hypothesis was proposed. The wave telescope technique was discussed to investigate the spectral properties of turbulence.

Large and small scales in turbulence:
Different methods for the reconstruction of magnetic fields were presented (linear and quadratic reconstruction, radial basis functions, timesync, Taylor expansion). Some applications require slowly varying fields, others require the vicinity of a null point, as in a reconnection event. Bilal Khan presented novel insights into how large-scale magnetic fields determine small-scale magnetic reconnection properties. Interesting discussion stemmed from Lily Strus comment on the emergence of an inverse cascade, the quantities that undergo this process and the dimensionality of the problem.

Prospects:

Measuring multi-scale energy transfer and dissipation in turbulence:
Moving to novel methods that can trace multi-scale energy transfer, beyond the current limitations of fixed-scale multipoint constellations. How can we picture the pathways of energy conversion across scales and directions with multiscale missions? Advancements are shown by the recent LPDE technique. The Liouville Mapping technique, presented by Rui Huang and Greg Howes, was highlighted as a method to characterize dissipation signatures in velocity space.

Space-time evolution and Taylor’s hypothesis:
Using multipoint multiscale measurements, the space-time evolution of turbulence can be investigated without additional assumptions. How will such new analysis methods improve the current understanding of turbulence modes’ evolution?

Large and small scales in turbulence:
With multiscale constellations, fewer assumptions on time stationarity and spatial gradients are needed. Will we be able to picture the magnetic fabric of the solar wind?

Session Description

Rohit Chhiber (NASA GSFC and U Delaware), Sam Badman (Center for Astrophysics, Harvard & Smithsonian), Craig DeForest (SWRI, Boulder), William Matthaeus (U Delaware)

The transition from sub-Alfvénic to super-Alfvénic flow in the solar wind occurs at a location that has been variously referred to as the Alfvén radius or point, the Alfvén surface, and the Alfvén zone. Other important transitions, including the rise of the frame-independent plasma beta parameter to near unity, occur in this same general altitude range. Regardless of the morphological details of this transition, it can be meaningfully interpreted as a boundary between the solar corona and the rest of the heliosphere, with several important differences between the physical processes that occur in sub-Alfvénic and super-Alfvénic domains. The Parker Solar Probe (PSP) mission has accumulated a wealth of in-situ observations of sub-Alfvénic solar wind during its recent solar encounters, and the PUNCH mission will provide unprecedented remote imaging data focused on this region. The time is therefore ripe for the SHINE community to engage in an exploration of what we understand about the Alfvén zone, and of the outstanding open questions that remain. We welcome contributions that employ in-situ and remote observations as well as analytical and numerical modeling to address these questions.

• What is the global structure of the Alfvén zone/surface, in terms of average altitude, “thickness”, 3D shape, and how this structure evolves with dynamic solar activity both in a steady sense and in relation to solar transients?
• What are the important differences in physical processes occurring on the “two sides” of the Alfvén zone, i.e., in sub-Alfvénic and super-Alfvénic solar wind? This may include differences in turbulence properties, wave-particle interactions and instabilities, energetic particle transport, switchbacks, and angular momentum transport.
• What are the implications of our knowledge of the solar Alfvén zone for the atmospheres of other stars and for space weather in exoplanetary systems?

Progress and Prospects Report

Scene setting speakers: Steve Cranmer (U Colorado Boulder), Alison Farrish (George Mason University and NASA Goddard)

Reviewed our current understanding of the Sun’s Alfven surface/zone and its significance as a boundary separating the corona and the rest of the heliosphere. Discussed remaining open questions and application of this knowledge to other stellar systems. Set the stage for relevant analyses of current and future data from Parke Solar Probe and PUNCH.

Overarching science questions to be addressed in the session were Q1: What is the structure/shape/dynamics of the Alfven surface. Q2 : What different physics operates above and below the Alfven surface. Q3: What are the implications of this knowledge for other star systems.

The first scene setting talk by Dr. Cranmer was titled “The Frothy Alfvén Surface: What Have We Learned? What Do We Still Need to Know?”, and focused discussion on Q1 and Q2.
— The distinctions between the Alfven surface and other neighboring boundaries such as the sonic surface, plasma beta=1 surface, PFSS source surface were discussed.
— What and how PUNCH will add to our observational dataset was discussed. Specifically, PUNCH’s methodology of tracking Sunward density blobs as a way to locate the Alfven surface was queried – the frequency/filling fraction of such structures was mentioned and contrasted to lack of Sunward propagating structures in Parker Solar Probe (PSP) data. The filling fraction in historic data is small but PUNCH may shed new light! The question of whether turbulence would “mix up” Sunward blobs, thus complicating their tracking was discussed. Methods of “counting” field lines across the Alfven surface through PUNCH image processing was discussed and related to sub- vs super-alfvenic switchback generation.
— Implications of the transition from subAlfvenic to superAlfvenic flow for various heliophysical phenomena (switchbacks, plasma heating, SEP transport, angular momentum) were highlighted.

The second half of the session was led by Dr. Farish with a scene-setter titled “Expanding the Alfven Surface Concept to Other Stellar Systems”, addressing Q3.
— The discussion was driven largely by interested heliophysicists asking clarifying questions about some basics of stellar physics and observational astronomy, such as what observables are used as measures of stellar activity. Key differences (synergies) such as the difficulty of measuring a single star over a long enough time to see stellar cycle activity and ease of measuring many stars of different types were highlighted.
— Mass and angular-momentum loss and long-term stellar evolution was identified as a very clear link between Alfven surface measurements at the Sun and stellar physics
— The interplay of sub-Alfvenic orbits with exoplanet habitability was discussed with analogy to the Jupiter-Ganymede Alfven-wing system.

In the current state of the field, we have the capability of modeling, directly measuring, and understanding the Alfven surface beyond its inception as a single critical point or infinitely thin surface. We can now very concretely measure not just its average distance from the Sun but its thickness/“frothiness” and departures from spherical symmetry. It is early days in studying the different physical regimes in sub- and super- Alfvenic regimes but there are exciting hints both of expected differences and surprises. Our observational dataset is bound to increase dramatically in the immediate future, thanks to PSP and PUNCH. This makes the topic worth revisiting in a SHINE session after a couple of years. There are ample opportunities for stellar-solar connection work including exoplanet habitability – these opportunities are not very well known across the SHINE community but provoke lots of interest!

Session Description

Phillip Hess (NRL), Christina Kay (APL), Erika Palmerio (PSI)

Improved spatial and temporal resolution and unique multi-spacecraft configurations have allowed coronal mass ejection imaging to move beyond merely tracking leading edges and fronts. A number of smaller scale structures within the CME body have been seen in instruments such as PSP/WISPR, SolO/SoloHI, SolO/Metis and GOES/CCOR1. This capability is only expected to grow as Solar Orbiter leaves the ecliptic and as data from the PUNCH mission and CCOR2 become available. The central question of this session is: what do these smaller features tell us about the physical processes which form coronal mass ejections and govern their global evolution in the heliosphere? 

How do apparent circular cavities in images at larger heliocentric distances relate to possible flux rope structures seen in the corona, near the Sun, and what does that say about the extent to which a CME from the Sun can really be called a flux rope structure?

MHD models have been developed, and synthetic images created, to attempt to re-create observations from imagers like LASCO, SECCHI and SDO and have largely been successful at creating realistic macroscale CME structures in these synthetic images. Of the micro- and mesoscale structures now being imaged, what are the models capable of resolving and what is currently missing? 

Progress and Prospects Report

Scene setting speakers: Cecilia Mac Cormack (CUA/GSFC), Ben Lynch (UCLA)

The main scientific points of the session can be sumarized as follows:

The classic CME ‘three part structure’ is an over-simplification based on limited observations, and new data have revealed that the structure is far more complex than this for most events

Going along with part 1, the GCS model for determining CME shape is far too simplistic to be considered a realistic physical representation for a CME. It can still be a useful tool for providing a rough idea of size, speed and propagation direction, but to truly reconstruct a CME in the corona (with higher-resolution imaging) and heliosphere more complex models need to be developed

MHD models in their current form are capable of reproducing, at least superficially, many of the mesoscale features seen in images from instruments such as WISPR and SoloHI, and are vital for helping interpret the underlying magnetic features of structures imaged in white light for generic events. However, there are still a number of uncertainties in these models, and both the models and inputs need to be improved to make modeling specific events consistently reliable.

In terms of future research directions, the biggest takeaway is that a more reliable method of physically determining CME structure in remote sensing images is needed. We do not know whether it is feasible to have such a model in place by the next meeting, but I think a future session devoted to this idea and discussing the best way to proceed in determining the underlying CME structure may be useful. A future session could focus on whether making specific improvements to a geometric shape is best or whether we need to break free from this form of reconstruction and explore more modern techniques.

Session Description

Emily Mason (Predictive Science Inc.), Micah Weberg (U.S. Naval Research Laboratory)

Coronal holes – the large, EUV-dark regions of open field in the solar corona – are of critical importance to solar physics, as the undisputed origin point of the fast solar wind, and a sometimes-disputed origin point of the slow solar wind. In recent years, a great deal of focus has centered on the boundary regions of these structures. It is generally accepted that the bright borders that are visible in EUV are not representative of the precise location of the actual open/closed boundary, nor can they account for the total open flux that fills the heliosphere. Methods have been developed to detect or derive the boundary using magnetic models, FIP calculations, image processing techniques, etc., yet many open questions remain. The purpose of this session is to bring together theorists, observers, and modelers to discuss their perspectives on coronal hole boundary determination, and then move towards a consensus on what is still lacking in order to bring closure to open questions on the open/closed boundary.

1. Does the open/closed boundary have a physically significant width?

2. What would constitute the “smoking gun” for defining the open/closed boundary in observations?

3. If the answer to 1 is “yes:” does the region have a physically-driven width at all times, or does the width come from a line that sweeps out a region as a function of time?

Progress and Prospects Report

Scene setting speakers: Karin Muglach (CUA/NASA GSFC), Jon Linker (PSI)

The main theme was to get modelers and observers to discuss current terminology and the state of the art of coronal hole boundary study. The goal was to move towards a more unified concept of what characterizes a coronal hole boundary and bring observational and modeling terminology into closer alignment.

The single biggest takeaway is that the traditional observational definition of a coronal hole as a “dark structure seen in the EUV” has outlived its usefulness to some extent. Both observers and modelers have a greater interest in identifying open flux regions, which may or may not appear dark in emission for various reasons (obscuration, intermittently open field, various time-dependent heating phenomena), most importantly for identifying solar wind origins and composition. While these open field regions are often contained within the boundaries of the old definition, it is no longer sufficient.

A major point that was brought up in the discussion is that the definition, shape, and physics driving the coronal hole boundary are all largely functions of height — they look very different at the photosphere vs. various levels of the corona. This in turn affects the open flux derived by various methods, whether they depend upon emission or magnetic field measurements.

The importance of time dependence was another recurring theme. Coronal hole boundaries evolve with time as differential rotation and interchange reconnection maintain or change the open/closed boundary, and the time and spatial scales upon which these mechanisms occur occupy a fairly broad range. High-resolution MHD studies of coronal holes also show that the open field region may actually be very small and fragmentary at the photosphere, which adds additional temporal considerations as small open flux bundles are jostled around. Time dependence is also important for solar wind studies of plasma origins and composition — how much open field participated in interchange reconnection, etc. Observationally, determining the boundary vs. the “inner” portion of a coronal hole is important for wind studies, and recent evidence rather consistently points to a characteristic boundary region width of about a supergranule.

Finally, a large portion of the session involved discussion of the S-web, as it relates to coronal holes. Such maps can be derived from observations or modeling, and show where you’re most likely to be sampling solar wind from a coronal hole boundary vs. deep within the coronal hole. Lots of time was spent on how to interpret these maps.

There was a general takeaway that S-web maps could be used more broadly in the field to inform solar wind studies. There was brief discussion of a few early machine learning attempts to address coronal hole identification with various datasets, but there was a good deal of skepticism about the underlying assumptions behind such previous studies. Many attendees expressed interest in greater focus on open field measurements and extrapolations in the corona, and on time-dependent processes (i.e., interchange reconnection at/in the boundary).

A future session on the temporal evolution of coronal holes would be beneficial, given the extensive discussion on how time-dependent processes affect both observations and modeling of the coronal hole boundary.

Session Description

Nishtha Sachdeva (University of Michigan) , Prateek Mayank (SWx TREC, University of Colorado, Boulder)

As solar activity increases, the likelihood of successive CMEs interacting in the interplanetary medium increases, potentially leading to prolonged geomagnetic impacts, as seen during the May 2024 Gannon storm. Despite advances in observations and modeling, the nonlinear coupling of multiple CMEs remains poorly understood, limiting space weather forecasting. This session aims to explore the underlying phenomena, including reconnection, reverse shocks, and energetics, that govern complex CME-CME interactions to improve our predictive capabilities.

1. Physical Mechanisms & Evolution: What physical processes dominate the interaction and evolution of successive CMEs as they couple or collide?

2. Origins to Impacts: How do the initial properties of CMEs and their sources (e.g., homologous or sympathetic) influence their geoeffectiveness?

3. Case Study & Prediction: How can we improve the forecasting of CME-CME interactions, as demonstrated by events like the May 2024 Gannon storm, through better data strategies, modeling tools, or more effective predictive metrics?

Progress and Prospects Report

Scene setting speakers: Evangelos Paoris (JHU/APL) & Noe Lugaz (Univ. of New Hampshire)

The goal of the session was to re-initiate the discussion about the observations and modeling of interacting CMEs. It was structured around three stages: pre-eruption, post-eruption signatures, and the interaction phase, with emphasis on the community’s complex observational and simulation efforts.

Major geomagnetic events are mostly a result of interacting CMEs. In the current era of unprecedented multi-viewpoint & multi-spacecraft observations, it is worthwhile to focus our attention on understanding these phenomena using data & modeling techniques. Major discussion points:

It may be easier to use active region signatures to predict the second eruption (after the first CME) and the second to last eruption rather than all CMEs associated with a storm.

What are the key observations that may be useful as early indicators and what drives the delay in eruptions?

Challenges in using white-light images and in-situ data to detect interacting structures.

Complexity in the internal structure of interacting CMEs.

How simulations can be utilized to understand the global interaction between CMEs & shocks?

The session discussion concluded that a statistical study is needed to quantify the likelihood of multiple eruptions and their associated geo-effectiveness.

Since these events are inherently quite complex, breaking the problem into smaller achievable goals may be a better strategy – for example, looking at active region data for identifiers for multiple/delayed homologous & sympathetic eruptions.
So far mostly case studies have been done for such events, a physics-based understanding with a statistical approach is required.

For future session, we may propose to focus on a specific topic related to interacting CMEs – for example, detailed physical understanding of interaction, geo-effectiveness and the impact of individual characteristics of the interacting CMEs.

Session Description

Abril Sahade (Heliospheric Physics Laboratory, NASA GSFC), Cecilia Mac Cormack (The Catholic University of America)

Solar eruptions release large amounts of solar plasma and more intense magnetic fields into the interplanetary medium than the surrounding environment. These events are usually observed in the lower corona as flares and/or prominence eruptions, and then in white-light images of the upper corona as coronal mass ejections (CMEs). Later, in-situ measurements indicate the arrival of the corresponding magnetic flux rope to a spacecraft. In this new era of solar observatories (e.g. Solar Orbiter, Parker Solar Probe, Bepi Colombo), we count with more information than ever to increase and challenge our understanding of the evolutionary process of eruptive events. To understand the complete evolution of the magnetic systems we need to not only combine the observations but to explain them under a common theoretical frame. Combining observations and modeling uncover a new path for a deeper understanding of CME evolution and internal structure.

What can we learn from numerical/operational modeling and which are the main
issues at the moment of matching real life and simulations?

How can we improve the reliability of these models?

Which are the advantages and possible improvements in this era of multi-view
analysis and high-performance simulations?

Progress and Prospects Report

Scene setting speakers: Nishtha Sachdeva (Michigan University) – Christina Kay (APL)

This session explores the insights gained from numerical and operational modeling, highlighting both their potential and the current limitations faced when aligning simulations with real observations. It brings up the different approach between theoretical and operational models, and the strategies to enhance model reliability, including improved calibration methods, integration of real-time data, and robust validation techniques. Lastly, it highlights the richer perspectives obtained with multi-view analysis and high-performance simulations that can increase the understanding of CME evolution.

We discussed how multi-viewpoint observations both challenge and enhance our understanding of this complex system. While they often complicate the picture, they also provide opportunities to improve our modeling—both for operational forecasting and scientific research.
The discussion was highly productive and covered many important aspects. We highlight a few key points here:

Operational Models: Most operational models initiate CME evolution at about 0.1 AU (~21 solar radii), by which point the CME has already undergone significant rotation, deflection, and deformation. Despite this, many models insert an idealized CME—often lacking a magnetic structure entirely. In such cases, the CME’s arrival time and evolution are driven mostly by background solar wind conditions.

Even when more advanced models are used, we face a significant observational gap between ~15 solar radii and 1 AU. Bridging this gap is crucial, and missions like Parker Solar Probe, Solar Orbiter, and PUNCH hold promise in this regard. Ideally, initiating CME evolution at 1 solar radius would yield the most accurate modeling, though this approach is more resource-intensive.
Numerical MHD Modeling: When simulating real events, we face persistent challenges in reproducing observed CME behavior from the low corona. This led to several critical questions: Are our magnetic field inputs the issue? Is the assumed flux-rope model inadequate? More importantly, what can we learn from simulations that do not match observations? Which features are consistently reproduced—and which ones are not?

From a scientific perspective, improving our understanding of CME evolution requires deeper integration of various observational inputs—including those less commonly used, such as particle detections, radio emissions, spectral analysis, and imaging of the inner heliosphere. Collaboration with solar wind modelers is also essential. Such synergies will not only enhance our ability to model CME propagation more accurately, improving operational forecasts, but will also help address the largely unexplored interplanetary evolution phase—particularly the observational gap region.

Future Sessions:

Given the new observational data from Solar Orbiter, Parker Solar Probe, and PUNCH, and the need for interdisciplinary collaboration, a highly relevant topic for a future session is “The Inner Heliospheric Evolution of CMEs.”

We must better understand how CMEs transition from structured eruptions near the Sun into large, interplanetary phenomena interacting with the solar wind. This discussion should involve experts in solar wind physics, numerical modeling, and observational analysis. Bridging this “hidden” phase of CME evolution is critical—and the latest missions are beginning to shed (collect) light on this elusive region.

Session Description

Viacheslav M Sadykov and Griffin Goodwin (Georgia State University, GA), Liang Zhao (University of Michigan at Ann Arbor, MI), Henry Han (Baylor University, TX)

Physics-based numerical simulations are invaluable for understanding the processes and interactions within the Heliosphere. Such simulations provide the fundamental possibility to model the plasma phenomena based on the first principles, although sometimes experience limitations such as high computational costs, restricted exploration of conditions, and sometimes simplified physical assumptions that may not fully align with observations. Machine learning (ML), by contrast, offers powerful data-driven modeling and learning capabilities to uncover latent behaviors and structures by leveraging large amounts of data, and is highly efficient computationally once well-trained and deployed. However, its performance depends heavily on the quality and diversity of the training data and generally lacks explainability. Both approaches present distinct advantages and challenges. This session aims to explore strategies for integrating physics-based models with ML techniques to harness their respective strengths while addressing their limitations, enabling more accurate and efficient modeling of heliospheric phenomena.

1. How can the hybrid modeling approaches that incorporate both physics-based and ML components improve the capabilities of modeling the solar and heliospheric environment (with respect to the speed and accuracy of simulations) and contribute to developing explainable ML?

2. How can ML approaches serve as a scale-coupling bridge by learning embeddings from physics-based simulations to model small-scale processes (e.g., kinetic processes and turbulence) within large-scale heliophysics modeling efforts? Can we exploit transfer learning alongside multi-fidelity learning to enhance the generalization and scalability of these ML models?

3. How can the physics-based models assimilate the real observational data information using ML to inform them about the realistic heliospheric conditions or any physics missing?

Progress and Prospects Report

Scene setting speaker: Bala Poduval (Space Science Center, University of New Hampshire)

This session focuses on the topic of intertwining physics-based simulations and machine learning (ML) methodologies. Both are known to have advantages and disadvantages; physics-based simulations can model any event for any boundary condition, but can be very computationally expensive if ensemble modeling is needed. ML is very fast once trained, but is limited by (and therefore depends on) the data it was trained on. Finding ways to merge the two approaches is therefore beneficial. Specifically, we discussed the following questions:

How can hybrid approaches (that incorporate both physics-based and ML components) help us in heliophysics modeling?

Could ML approaches help inform the large-scale physics-based models about what is happening at smaller scales?

Can ML help to assimilate observational data into the physics-based models to improve the performance and predictions?

The first half of the session explored general aspects of machine learning (ML) in application to scientific research. The general questions discussed with the audience during the first half were:

What scientific problems can or cannot be (or do not need to be) tackled by ML? The audience converged on the point that, while there is a zoo of commonly used ML methods such as regression, classification, and dimensionality reduction, the choice of a particular technique should be problem-dependent.

How can the prediction of the ML model be validated and compared (question on the benchmark datasets)? It was reiterated that the predictions of models are often not comparable given the different data sets they are evaluated; therefore, a common benchmark is needed.

How can we look inside the ML ‘black box’ to ensure that the model prediction is meaningful? For example, it was shown that the feature importance analysis can enhance physical understanding of what the model pays attention to when making a prediction, and therefore gather insights about the physics of the phenomenon.

What metrics or measures can we use to evaluate ML performance? The audience discussed the classification (TSS, HSS) and regression (MSE) measures, as well as talked about other approaches like elastic measures.
During the second half of the session, the discussion became focused on bridging the simulations and machine learning. Specifically, the following topics were brought:

Physics-Informed Neural Networks (PINNs). There are several examples in Heliophysics, from NLFFF to full RMHD. The continuous nature of the predictions (grid-agnostics) of PINNs was emphasized as an advantage, while the adjustment to particular boundary conditions (and, therefore, scalability) remains in question.

Surrogate modeling. The audience discussed the case of ‘emulating’ (i.e., creating a surrogate) a physics-based model for energetic particle transport in the Heliosphere. It was emphasized that such an approach is not an improvement with respect to accuracy, but is intended to reproduce the physics-based model with all its imperfections for the sake of faster assessment and ensemble modeling.

Informing a large-scale physics-based model about small scales using ML. While this topic is widely applied in astrophysics, the applications in Heliophysics are limited. An example of Reynolds stress tensors for Large Eddy Simulations was shown. The audience emphasized that it is really important to see how the small-scale changes will affect the much larger scale’s result.

An example of assimilation of the observational coronagraph data into the simulations using ML was demonstrated. The ML can help down-select a particular ensemble member to aid the forecasting.

It was understood from the discussion that the application of ML to heliophysics problems is of broad interest overall. The audience emphasized that the incorporation of physical models into ML is still a major challenge, and the science in this direction is mostly in its infancy. Therefore, we can easily imagine the same direction of the session at the next SHINE conference that would track the recent progress of the community in this direction.

Session Description

Bin Zhuang (University of New Hampshire), Fernando Carcaboso (NASA Goddard Space Flight Center), Andreas J. Weiss (NASA Goddard Space Flight Center), and Shaheda Begum Shaik (George Mason University/Naval Research Laboratory)

Coronal mass ejections (CMEs) are large-scale transients and energetic expulsions that
have been studied over decades. They can be measured in situ, and there have been
continuous attempts to extract their local and global properties through analytical and
empirical models. While the diverse observational and modeling approaches have greatly
advanced our understanding of CME properties, the range of assumptions and techniques
can complicate the accurate understanding of these large-scale structures. Particularly,
some techniques might have the risk of being misused when interpreting the CME data
from the passage of a single or a few spacecraft. This session focuses on our current
understanding of CME physical properties by integrating multipoint in situ measurements,
models, and methods for a comprehensive view of CMEs, highlighting both the advantages
and limitations/caveats of the modeling efforts. It will also emphasize how different data
sources from multiple missions and instruments, models, and methodologies can be best
combined, compared, and validated to improve our overall understanding of CME physics.

(1) What physical properties and characteristics of CMEs can be derived from
currently available in situ measurements and models?

(2) In what situations may these
models with specific assumptions over-interpret the results or mislead our understanding
of CMEs?

(3) What do we expect to fill the gap of understanding the CME properties with
unique spacecraft constellations, and with combinations of CME, not only in situ but also
remote models (model synergy)?

Progress and Prospects Report

Scene setting speaker: Qiang Hu (University of Alabama in Huntsville)

The session discussed CME in-situ observations and models, and focused on the model
validation as well as the potential overinterpretation, misuse, or caveats when applying models to the data.

1) The session started with the topic of how to define a flux rope and it was discussed how to derive the axial and poloidal magnetic fluxes using on in-situ measurements.
a) The axial magnetic flux is difficult to determine because it depends on the model used and the boundary selection.
b) How to check the boundary selection and testing the model output: for example, it would be useful to check the balance of the calculated poloidal magnetic flux from the front to the end of the CME flux rope, or using a brute force approach to estimate boundary selection uncertainties.
2) The session then discussed the use of the deHoffmann-Teller (HT) frame → remaining magnetic field vanishes. However, as pointed out during the session, this is just an assumption of the model and can not be used as a criterion to identify CMEs.
3) Following the HT frame assumption, the session discussed how the CME dynamic evolution (e.g., expansion and aging effect) would affect the model output.
a) In-situ models always take temporal invariance assumption (quasi-static). However, for example, the magnetic field strength in the back part of the CME is at least 20% weaker than that in the front part due to aging. Thus, quasi-static models will inevitably incorporate uncertainties.
b) Some models use a single assumption, e.g., either force-free or non-force-free. However, CMEs can be complicated, with a portion belonging to a force-free condition and another portion being non-force-free.
c) For measurements obtained from PSP or SolO, which moves in the innermost heliosphere, quasi-static models for more dynamic CMEs may have larger uncertainties. The session discussed that, according to the current validation, it is still appropriate to use models with this assumption.
4) The session discussed a technique issue about validating the model output.
5) The session used a specific case (2023-12-01 CME) to further discuss using multiple spacecraft to validate models, model uncertainties, and comparison between single and multiple spacecraft modelings.
a) When inputting multiple spacecraft measurements into the model, what parameters are more relevant, or how to use these measurements to constrain the parameters, e.g., reduce the number of free parameters?
b) If there have been uncertainties in one spacecraft, whether or not additional inputs will result in larger uncertainties, especially when the model doesn’t fully capture the CME in-situ properties for the first spacecraft.
c) Using multiple radially aligned spacecraft will be helpful in resolving the CME aging effect.
6) The session finally discussed two relevant points: a) how the combination of Forbush decrease with MHD simulations and analytical models can help understand the CME properties, e.g., whether we could determine if a spacecraft is closer to flank or center of CME, and b) comparison of the CME properties with longitudinal proximity to the nose: remote and in-situ methods do not agree.

Session consensus: a) complex models are necessary if one really cares about the magnetic field configuration of CMEs: variability in the in-situ data can be attributed to 3D spatial variations, and b) multiple spacecraft datasets are necessary for model validation.

Future prospects: as described above, for the scientific part, it is worthwhile delving into the model validation with a) multiple spacecraft inputs, b) complex CME configuration assumption, and c) properly dealing with the aging effect of CMEs rather than continuing to use the quasi-static assumption. For future sessions, it would be good to propose a session by combining both remote and in-situ models and observations, especially focusing on what we can learn from the models and how to use different types of observations to cross-validate the model output.

Session Description

J. Grant Mitchell (NASA/GSFC), Georgia de Nolfo (NASA/GSFC), Alessandro Bruno (CUA & NASA/GSFC), Nicola Omodei (Stanford)

Solar flares are well known to accelerate ions and electrons to high energies. Many solar flares occur with a closed magnetic topology in which accelerated charged particles remain partially or totally trapped within the corona. In these cases, the secondary neutral emission (in particular X-rays, gamma-rays, and neutrons) produced in interactions of precipitating particles with the dense solar atmosphere is our only insight into these otherwise inaccessible events. Measurements of solar neutrons and gamma rays can yield, among other things, valuable information regarding the temporal and spectral characteristics of the acceleration and transport mechanisms. With different reaction thresholds, they offer a method for examining how flare particle energization evolves in time, and provide complementary insight into the composition of the chromosphere/photosphere and the parent particle population. That said, neutrons and gamma-rays are some of the least-studied products of solar flares, and are arguably the most difficult to measure with the necessary accuracy. Our 2023 session was aimed to give an important re-introduction of the field to the community including initial brainstorming on mission concepts. In this new session we plan to expand these topics with the goal of identifying key measurements and modeling to progress our understanding of solar eruptive events at the highest energies. 

1. What are the challenges of measuring flare neutrons with the world-wide network of neutron monitors? 

2. What is the state of flare-loop modeling and what advances are required to better understand this secondary neutron production? 

3. What can complementary measurements of hard X-rays, gamma-rays and neutrons tell us about the details of the flare energization process?

Progress and Prospects Report

Scene setting speakers: Jim Ryan (UNH), Nikolay Nikonov (University of Hawaii)

This session brought together researchers and an engaged cohort of students to explore developments in solar flare neutron and gamma-ray measurements, modeling approaches, and opportunities to use these measurements to better understand particle acceleration at the Sun.

Jim Ryan (University of New Hampshire) delivered a comprehensive opening presentation that established the scientific foundation for the session. His work illuminated the complex physics of solar gamma-ray production and provided a detailed description of Long Duration Gamma-Ray Flares (LDGRF). He presented mathematical modeling efforts while candidly addressing current model limitations. His presentation culminated with compelling evidence for simultaneous solar gamma-ray and neutron observations, highlighting how their complementary interaction cross-sections and distinct spectral and temporal signatures can revolutionize our understanding of solar flare acceleration mechanisms. What is missing in closing our understanding of particle energization are solar neutron observations.
Nikolay Nikonov (University of Hawaii) provided insights into ground-based measurement of solar neutrons at Earth, focusing on neutron monitors and ground-level solar neutron telescopes. His presentation described the challenges posed by free neutron decay, observable energy signatures at 1 AU, and reconstruction of incident spectra based on ground-level measurements.

Emerging Technologies and Novel Observations
The session featured two walk-on presentations that highlighted breakthrough capabilities:
– Rick Leske (Caltech) showcased measurements from the HET instrument within the ISOIS suite aboard Parker Solar Probe, presenting solar gamma-ray observations and potential neutron detection capabilities from humanity’s closest solar approach mission.
– Zigong Xu (Caltech) revealed neutron data from Chinese instrumentation deployed on the lunar surface.

The session’s forward-looking discussions identified new opportunities to advance the field beyond current limitations. Participants explored concepts including:
– Strategic lunar-based neutron monitoring leveraging the Moon’s unique observational advantages
– Advanced space-based neutron spectrometers currently in development, including detailed analysis of the unique engineering challenges posed by space-based neutron detection
– Innovative large-scale, simplified neutron spectrometer concepts designed for future flagship mission opportunities
To make progress we need to expand on modeling the flare loop to accommodate both high-energy and neutron emission, in addition to identifying solar contextual data that can better constrain these models. In addition, extreme solar flares and the attendant neutral radiation plays a key role in planetary habitability.

Session Description

Michael Terres (Smithsonian Astrophysical Observatory), Srijan Bharati Das (Smithsonian Astrophysical Observatory), Emily Lichko (Naval Research Lab), Sarah Conley (Princeton University)

The devil is in the details: The key to addressing fundamental questions related to heating, acceleration, and turbulence in the solar wind is an accurate representation of particle phase space velocity distribution functions (VDFs). The structure of solar wind VDFs elucidates the history and evolution of a plasma parcel from the low corona to the heliopause and beyond. VDF observations are often incomplete due to instrument limitations or because the measurements are performed in reduced phase space dimensions. Oversimplified bi-Maxwellian fits of such VDFs are inadequate to analyze multiple ion populations, plasma wave modes, instabilities, and other nonlinear phenomena that require well-resolved, non-equilibrium VDFs.

In response to this issue, there has been a recent surge of analytical, numerical, and machine learning-based techniques to maximize the information collected by in-situ observations of various plasma species. Careful cross-overs of such novel methods hold the potential to judiciously characterize smooth, high-resolution phase space measurements derived from coarse instrumental grids. These techniques open various pathways to quantify the energy transport, which are tractable primarily via numerical simulations. By integrating these innovative tools with wave-particle correlation methods, numerical solvers, and phase space entropy cascades, we are now able to investigate kinetic processes in detail from in-situ observations. Discussion in this session will be aimed towards the current state of novel data processing techniques, how these can bridge the gap between observation and theory/simulation, and finally, will address what future observations and coordinated strategies are needed to bring closure to long-standing questions in kinetic plasma physics.

1.) How do new reconstruction techniques enhance our understanding of wave-particle interactions and energy transport? 

2.) How can we leverage measurements from past and current instruments with state-of-the-art simulations to best prepare for future missions?

3.) What measurements are needed to bring closure to understanding the energy transport in the solar wind?

Progress and Prospects Report

Scene setting speakers: Davin Larson + Space Science Lab

This session focused on connecting modern numerical simulations with current observations. A large portion of this discussion focused on the challenges of extracting physical insight from incomplete or finitely measured velocity distribution function (VDF) measurements. While bi-Maxwellian fits remain a common baseline, they are insufficient for resolving the non-equilibrium features, beams, shoulders, and anisotropies that encode key kinetic features in the solar wind. The discussion centered on reconstruction techniques, observational constraints, and how we can responsibly push the limits of current data.

Davin Larson opened by framing key questions around wave energy content, the role of alphas, and whether surfaces such as β = 1 or the Alfvén critical point serve as meaningful physical boundaries. His remarks emphasized the importance of revisiting assumptions baked into both data analysis and instrument design. For example, SPAN-i’s limited field of view, particularly in deflected theta, poses challenges for recovering complete ion distributions, especially during switchbacks or near the current sheet. We were reminded that even familiar quantities, such as alpha-to-proton density ratios, can be misleading when parts of the distribution fall out of view. Davin’s scene-setting talk garnered a lot of active discussion, with many questions and comments from the audience. There was particular interest in the hammerhead VDF, which was first observed in the solar wind using PSP SPAN observations in Verniero et al. (2022). These lead to discussions on similarity (or possible connections) between such hammerhead distributions observed in the solar wind and crescent-shaped VDFs, which have been well observed using MMS in the magnetosheath. Davin finalized his discussion with several caveats to consider when interpreting particle measurements from SPAN-i and other electrostatic analyzers in the solar wind.

Several contributions explored both observational reconstructions, modern analytical techniques, and numerical simulations. Fernando Carcaboso presented a Legendre polynomial expansion approach to electron VDFs, highlighting the bi-directional trends associated with the solar cycle. Rui Huang led a discussion on the field-particle-correlation technique, focusing on its application to modern gyrotropic reconstruction techniques. Finally, Yogesh shared results from PIC simulation tracking beam-driven instabilities, highlighting the need for high-resolution plasma VDF measurements. These efforts highlight the importance of accurate, high-resolution measurements of particle distributions in the solar wind.

Uncertainty quantification was a major theme. Bowen and Azari’s use of Gaussian process regression (GPR) to generate uncertainty-aware reconstructions was discussed, although questions remain about the behavior of extrapolation and physicality. There was strong consensus that any method producing smooth VDFs from coarse data must make its assumptions explicit and provide a defensible uncertainty model. Partial moments, for instance, are often no better than poor fits unless at least half the distribution is in view.
Another recurring point was the issue of structure persistence. When is a one-count feature real? Can we trust a beam if the core is out of view? Are hammerhead-like structures signatures of fast-wave instabilities, or just artifacts of counting statistics? Verniero et al. (2022) was highlighted here, along with a discussion of how VDF structure correlates with RMS magnetic field variability, an axis along which future data products might be enriched.

There is an ongoing effort to make high-cadence alpha fits publicly available, with proton subtraction still in progress. There was also continued interest in having a simple bi-Maxwellian fit using joint SPAN and SPC data, even if it does not perfectly reflect the kinetic structure, but rather in the interest of getting accurate moments. These products will be critical for improving our understanding of composition-dependent transport and energetics. There was also interest in using QTN-derived densities as a constraint for VDF completeness; however, methods differ, and some neural network approaches are promising, although QTN data quality and accessibility remain limiting factors.

Looking ahead, the path forward is likely to involve targeted integration of high-resolution measurements, simulation-informed reconstruction, and robust error tracking. The group emphasized the need to constrain reconstructions with instrument response and to be selective about when moments or fits are meaningful. A combined data set with consistent treatment of magnetic field variability, viewing geometry, and density constraints would go a long way toward closing key gaps. Ultimately, it’s about knowing when the data are trustworthy and when it’s not.

This session generated several ideas for future discussions, particularly focused on the plasma conditions under which various plasma dissipation processes occur and the measurements needed to diagnose them.

Session Description

Sherry Chhabra (George Mason University/Naval Research Laboratory), Sam Schonfeld (Air Force Research Laboratory), Shaheda Begum Shaik (George Mason University/Naval Research Laboratory), Surajit Mondal (Center for Solar-Terrestrial Research, New Jersey Institute of Technology)

The newly released 2024-2033 Solar and Space Physics Decadal survey strongly endorses the Frequency Agile Solar Radiotelescope (FASR) as a high-priority NSF midscale infrastructure project. It emphasizes FASR for its ability to concurrently observe the solar transition region all the way to the middle corona in the radio regime with unprecedented imaging fidelity and dynamic range at high temporal and angular resolution. Although not solar-dedicated, the upcoming Square Kilometer Array (SKA) and Next-Generation Very Large Array (ngVLA) also have the potential for similar observations on an occasional basis. But how will these next-generation facilities help advance SHINE research? This session will start with a primer on FASR, how it builds from existing, pathfinder facilities (EOVSA, LWA, VLA, etc.), the novel and exciting science it will enable, and how FASR integrates with future ground-based observatories and the integrated HelioSystems Laboratory. This session will help hone the science cases for FASR through lively discussions of SHINE community science questions and how next-generation radio observatories can address them. 

1: How will the unique capabilities and novel measurements of next-generation radio arrays advance SHINE research?

2: What physical parameter constraints (e.g., volumetric magnetic field strengths, accelerated electron spectra, hydrogen emission measure, CME acceleration, etc.) probed by next-generation radio observatories, do you need to advance your science questions?

3: How can we integrate next-generation radio observatories into the HelioSystems Laboratory?

Progress and Prospects Report

Scene setting speakers: Dale E Gary (New Jersey Institute of Technology)
Sijie Yu (New Jersey Institute of Technology)

This session explored the scientific insights made possible by radio observations and how to integrate those into the existing understanding of a number of SHINE-relevant science questions. Dale Gary led the discussion during the first half of the session with a broad overview of the theoretical contributions radio observations can provide, along with a description of the capabilities and prospects for FASR (Frequency Agile Solar Radiotelescope) and other next-generation radio arrays. Sijie Yu set the scene during the second half of the session by highlighting some recent results from the existing EOVSA (Expanded Owens Valley Solar Array) and OVRO-LWA (Owens Valley Radio Observatory-Long Wavelength Array) to prompt conversations about advancing SHINE science questions with existing radio data.

The conversations in the session were wide-ranging and covered many science topics. One recurring feature of these conversations was the important complementarity of the radio observations and the difficulty of interpreting them in isolation. It became clear that they are most valuable when paired with diagnostics observed in other parts of the electromagnetic spectrum and interpreted in the context of models that explicitly consider the physical mechanisms responsible for radio emission.

There was significant discussion about how, through the observation of gyroresonance emission layers, EOVSA (and eventually FASR) can measure the magnetic field strength in the corona both during flaring and quiescent times. By combining these measurements with magnetic field measurements at the photosphere (and, if available, in the chromosphere) along with coronal field extrapolations, it is possible to obtain a more accurate distribution of coronal currents (e.g., with the CICCI or MBSL) than is available now.

We had a long conversation about how hard X-ray and microwave observations of nonthermal particles in flares provide complementary information about their acceleration and dissipation. Hard X-rays probe electrons precipitating into the chromosphere while microwave observations measure electrons trapped in the post-flare loops for an extended period. Using both wavelength regimes to study these populations in more detail may provide insight into the energy budget of flares and where exactly in the solar atmosphere that energy is deposited.
We also repeatedly returned to the unique diagnostics that microwave and decimetric observations can provide for CMEs and their associated shock physics. Gyroresonance observations provide a measurement of the CME magnetic field that can be compared with the underlying active region and is a crucial constraint for flux rope insertion and propagation modeling. The radio emission often differs significantly from white light observations of launching flares, indicating a discrepancy between the spatial extent of high-energy particles and the bulk plasma, which may reveal important information about CME initiation. Finally, Type II radio bursts are associated with CME shocks, and studying their properties can constrain shock geometries and the associated magnetic field.

The radio session at SHINE is unique in that radio data can complement and provide context for a vast range of research topics in heliophysics. But these data are currently underutilized by the larger SHINE community. As a result of this (and our previous) session, we have seen growing interest in the community for using said data. From the rich discussions during the session, we expect collaborations that will advance a wide range of SHINE science. One possibility for a future session is to build on these collaborations for a more focused session exploring a particular topic in detail, e.g. early CME structure and evolution. We also envision future sessions focusing on strengthening the user community to continue building momentum for a future where FASR contributes to all areas of SHINE research.

Session Description

Shea Hess Webber (Stanford), Bill Abbett (Berkeley) — both COFFIES

Traditional solar interior models assume an environment of high beta, where the fluid pressure is dominant. However, the photosphere is not only a transition region to magnetic pressure dominance, but the plasma beta in this region can also fluctuate with time and location. It is unclear how this (and other) regions of beta transition impact models (e.g. flux transport, MHD) and observations (e.g. helioseismology).

1) How does the transition of the plasma beta from within the convection zone to the solar atmosphere impact our models and observations?

2) Do we need to be taking this transition region into greater consideration in our physical understanding of the interior and atmospheric regimes?

3) If so, how do we do so effectively?

Progress and Prospects Report

Scene setting speakers: KD Leka (NWRA), Mel Abler (SSI)

This session focuses on the gap between two regions of the Sun that are traditionally treated as disparate regimes, when in reality neither the solar interior nor the solar atmosphere are closed systems. We need to better understand the connection between these two physical environments and the varied expertise and open discussion that SHINE provides is ideal for having this conversation. It allows for new ideas to come from fresh, cross-disciplinary eyes.
1) How does the transition of the plasma 𝝱 from within the convection zone to the solar atmosphere impact our models and observations?
2) Do we need to take this transition region into greater consideration in our physical understanding of the interior and atmospheric regimes?
3) If so, how do we do so effectively?

The first half of the session explored the plasma beta from the solar photosphere up to the solar wind, corresponding to different plasma and magnetic field interaction regimes. The specific science topics that were discussed included:

– Convection implies high-𝝱, but high-𝝱 does not require convection.

– The chromospheric environment, where the transition from high-𝝱 to low-𝝱 happens, remains extremely challenging to model (given sharp changes in temperature, density, non-equilibrium of radiation, ionization states, etc).

– The 𝝱=1 transition affects the wave propagation in magnetized plasmas, therefore posing questions on mode propagation and conversion, and impact on helioseismology.

– Determining 𝝱 may be difficult due to the observational constraints. For example, the observational inference of the magnetic field (even photospheric) is not straightforward and depends on resolution and methodology. In some 𝝱 regimes, the needed quantities (magnetic field strength, plasma density, and temperature) are more readily available than in others as well.

– In the regions where 𝝱~1 (like the solar wind), the spatial homogeneity of plasma parameters plays an important role. Modeling is simpler in spatially homogeneous plasma, without the fine structures.
The second half of the session was focused on exploring the 𝝱 regimes with laboratory experiments, specifically what is accessible, how is it accessible, how solar & heliophysics scientists should think about plasma experiments, and how lab experiments can be used to answer pressing problems in solar & heliophysics. The specific science topics that were discussed included:

– MagNetUS – a magnetized plasma research ecosystem – provides a collaboration bridge between heliophysicists and plasma experimentalists. The ideas can be proposed via white papers, and then a collaborative work on the particular experiment design happens. The key physics bridge is the plasma dimensionless parameters (and plasma 𝝱 is one of them) that are targeted to be matched as closely as possible between two environments.

– Lab experiments are definitely augmenting and complementing the heliophysics expertise. For example, there are contributions to the understanding of plasma wave damping, reflection, propagation, and magnetic reconnection, transferable to the heliophysics realm. There was an active discussion with respect to the plasma composition and spectroscopy capabilities, experimental modeling of wave damping and turbulence.

– Experiments come with limitations which should be kept in mind, including challenges with matching several dimensionless numbers simultaneously, lab-specific effects (interactions with the boundary, different gravity environments, etc). In addition, access to the detailed description of the experimental facilities and the produced data could be a problem, but the work is in progress.

A follow-up session on understanding plasma 𝝱 could easily address:

– very specifically interpreting the photosphere boundary in the context of helioseismology, which was not so extensively discussed in the session;

– A deep dive into lab experiments aimed at a particular SHINE regime (solar wind, denser solar atmospheric plasma, wave propagation in both environments)

– Waves across the plasma-𝝱 regimes, a topic that resonated throughout the entire session.

– Continuation of this exercise focusing on understanding the chromosphere and related 𝝱=1 transition.

Session Description

Ruizhu Chen (Stanford University); Bibhuti Kumar Jha (Southwest Research Institute, Boulder); Prateek Mayank (Space Weather Technology, Research and Education Center, University of Colorado Boulder)

Most models for forecasting space weather or solar wind rely on comprehensive observations of the entire Sun, encompassing both the Earth-facing near-side and the far-side photospheric magnetic map, as an inner/lower boundary condition. Observations from multiple-vantage points (eg. STEREO, Solar Orbiter) has significantly improved our understanding of solar dynamics and enhanced our forecasting capabilities. However, direct, continuous far-side observations are currently unavailable and will not resume until the STEREO satellites return to a far-side orbital position in coming years. In the interim, helioseismic far-side imaging and Surface Flux Transport (SFT) modeling offer valuable near-real-time estimates of the full sun including far-side estimation of the photospheric surface magnetism. Incorporating these products into forecasting models has the potential to significantly enhance the accuracy of space weather predictions.

1. How accurately can we observe and model the solar far side using helioseismology, SFT, and other approaches?

2. What new insights into solar activity and magnetic evolution can multiple-vantage observations and far-side modeling provide?

3. How can far-side observations and modeling enhance space weather predictions, including coronal and solar wind forecasts?

Progress and Prospects Report

Scene setting speakers: Junwei Zhao, Stanford University, Evangelia Samara, NASA Goddard Space Flight Center

This session explored current capabilities and challenges in observing and modeling the solar far side Active Regions (ARs), particularly how these efforts inform the Surface Flux Transport models (SFT) and the space weather forecasting. The discussion brought together helioseismology experts, SFT modelers, and forecasters, focusing on practical use and future development of far-side data products.

Progress

Helioseismic Far-side Imaging: Helioseismic maps rely on low-degree modes (ℓ ≈ 50–300), limiting resolution to ~10°. The integration time requirements lead to asymmetric uncertainty in East and West Limb, with East being more accurate. Two techniques, time-distance and holography are available; however the end users are encouraged to compare them to understand the strengths and weaknesses of both of them.

Surface Flux Transport Models (SFTMs): Differences between SFTMs often stem from how physical processes are implemented. The method of incorporating far-side data may have less impact than model assumptions. Solar Orbiter/PHI data is beginning to be assimilated, though validation is ongoing.

Impacts on Coronal Modeling: Adding or omitting far-side information can significantly affect PFSS and MHD model outputs, particularly streamer locations and coronal hole boundaries . These impacts are strongest when new complex AR emerges near existing ARs or weak remnant flux.

Prospects

Improve Far-Side Observability Through Cross-Calibration and Method Integration:
Combining helioseismic time-distance and holography techniques with both HMI and GONG, alongside Surface Flux Transport Models and machine learning-derived magnetic maps, could offer a path toward improving detection accuracy and modeling of far-side active ARs. Future work should focus on combining far-side data from multiple sources as well as STEREO and Solar Orbiter observations for validation.

Quantify Sensitivity of Global Magnetic Models to Far-Side ARs:
Participants emphasized the need for systematic studies to assess when and where far-side regions significantly impact global coronal structure and solar wind predictions. Targeted ensemble modeling experiments (e.g., varying AR location, size, orientation, and tilt) would help us to guide operational use of far-side inputs.

Develop Ensemble and Perturbation-Based Forecasting Frameworks:
Given the inherent uncertainties in far-side magnetic field estimates, ensemble modeling approaches—possibly involving SFT, PFSS, and global MHD—were suggested to explore forecast variability. Sensitivity studies that perturb magnetograms with inferred far-side ARs could help determine when their inclusion improves space weather forecasts.

Session Description

Brian Welsch (University of Wisconsin – Green Bay);  Mike Wheatland (University of Sydney, NSW, Australia); Yang Liu (Stanford University); Jon Linker (Predictive Science)

Coronal electric currents are believed to supply the energy released in CMEs and solar flares.
Despite these currents’ central role, however, we possess limited knowledge about (i) their structure and (ii) how they evolve before and after CMEs / flares. However, the recent application of Gauss’s separation method to observations of the Sun’s photospheric magnetic field shows promise for substantially improving our understanding of coronal currents and CME-associated changes. What can this and other observational methods teach us about the nature of coronal currents and their evolution associated with CMEs and flares? 

What can inferences about coronal currents derived from observations, photospheric and otherwise, teach us about the structure of and evolution of currents in CME source regions? 

Where and in which direction(s) do currents flow?

How do these currents evolve around the times of CMEs and flares?

Progress and Prospects Report

Scene setting speakers: Johnthan Stauffer, Naval Research Lab, Jon Linker, Predictive Science Inc.

Recently, two different methods have been presented (Schuck et al. 2022; Titov et al. 2025) to partition (or to decompose) the vector magnetic field at the solar photosphere (i.e., vector B as a function of space on that 2D surface) into three separate vector fields, each from source currents in distinct locations: currents interior to the surface, currents across the surface, and currents exterior to the surface. The session’s main goals were to clarify for participants how these partitions work, discuss the information they might yield about the magnetic structure of CME source regions, and explore the physical implications of partitioning the fields using these two different methods.

Progress

Many topics were raised, but themes that were discussed more extensively are listed here.

THEME 1: The partition methods’ inability to localize currents beyond “above” or “below” the separation surface was discussed. For instance, currents above the surface could flow just above it, or quite far above it. The portion of B at a point on the photosphere due to exterior currents is equal to a volume integral of current densities over the exterior volume, but knowing the value of an integral does not determine the integrand.

THEME 2: There was extensive discussion of magnetic field changes observed in flares. Some theorists (e.g., Melrose 1997) and observers (e.g., Janvier et al. 2014) have proposed that flares cause the heights of coronal currents to decrease. Lowering heights of currents above the photosphere would plausibly cause changes in the photospheric vertical magnetic field; but these also might be inhibited due to the photosphere’s high conductivity & high inertia. Observations of significant changes in horizontal photopheric fields during flares are well known. In contrast, observations typically show smaller, less coherent changes in vertical photospheric fields during flares. Anecdotally, in a small sample of strong flares, more substantial vertical-field changes seem to occur over longer intervals (2-3 hours) after flares; but it is challenging to distinguish “flare-associated” vs. “normal” magnetic field changes outside of flaring intervals. The strong persistence of the photospheric vertical field when flares/CMEs occur makes the photosphere a natural place to partition B; in comparison, a CME might totally change the vertical magnetic field at, say,1.2 solar radii, suggesting that partitioning the field there (if it could be measured!) would not make physical sense.

THEME 3: Regarding horizontal field changes due to flares, it seems that the toroidal field component, which is due to vertical currents across the photosphere, tends to increase due to eruptive flares, implying currents across the photosphere increase. Why photospheric vertical currents should increase is not currently understood.

THEME 4: Aspects of chromospheric vector magnetic field observations were discussed, including their utility for isolating current locations with multi-height measurements and the difficulty of applying these partition methods on the corrugated, tau = 1 surface expected in spectral lines formed significantly above the photosphere. (Corrugations are also significant for photospheric lines on smaller horizontal scales.)

Prospects

THEME 1, currents’ heights: techniques to reduce this indeterminacy in currents’ heights, presumably requiring additional, distinct observations, would be helpful. Radio observations (e.g., FASR) were mentioned in this context.

THEME 2, flare-related vertical-field changes: A statistically meaningful sample of observations of vertical field changes associated with flares, esp. compared with control (or baseline) observations well separated from flare times could clarify whether, and if so how, flares affect vertical fields.

THEME 3, flare-related vertical current changes: As with the previous theme, observations of flare-associated vertical-current changes associated with flares could i

THEME 4, chromospheric vector magnetic field observations: Despite the problem of the corrugated tau=1 surface, these merit investigation

Session Description

James Ryan (UNH), Joe Giacalone (U Arizona), Ashraf Moradi (U Arizona), Alessandro Bruno (GSFC)

Neutron monitors have become a key tool of NSF in the studies of space weather. Their impact on aviation is under appreciated. With the recent investment by NSF into neutron monitors, we want to get ideas, input and discussion from the larger community.

As in the description, “Detecting them, measuring them, assessing the danger they pose, notifying concerned parties and predicting them are all subjects of this session.”

Tyler Eddy, Liang Zhao, Jim Raines, and Aidan Nakhleh

The 2024 Heliophysics Decadal Survey’s (HDS) highest priority for NASA’s Living With a Star (LWS) program is the Solar Polar Orbiter (SPO) mission concept. A polar orbiter around the Sun will be able to produce unprecedented measurements of the Sun, the solar wind, and the magnetic field in the polar regions in order to understand the origin of the solar magnetic dynamo and how the magnetic field drives solar activity and shapes the heliosphere over the course of the solar cycle. The HDS included the following instrument suites in it’s recommendation: doppler vector magnetograph, EUV imager, white-light coronagraph, heliospheric imager, magnetometer, ion-electron spectrometer, ion mass spectrometer, and energetic particle suite. This session will discuss the specifics of these instrument designs in addition to their capabilities and limitations in addressing the science questions outlined by the survey.

What measurements, remote and in situ, are necessary to meet the stated science goals of the proposed LWS Solar Polar Orbiter mission?

What instrument suites will match the best performance capabilities (e.g., range, resolution, life expectancy) to the necessary measurements defined above?

Presentations

Call for Community Input to LWS Focused Science Topics

Notes

Download docx of notes

Solar Poles Mission Town Hall: panel led by Tyler Eddy and Ayden.

Notetaker: Masha Kazachenko

How do we design the next heliospheric pole mission? 

1. Panel Member Nour Raouafi:

Brene Brown: vulnerability is the birthplace of innovation, creativity and change.

NASA HPD Priority science questions:

1. What drives the constant change we observe on our Sun.
2. What are the impacts of this dynamic space system on humanity?
3. What drives the changes in near-Earth space, the planetary space environments, the heliosphere and the interstellar medium.

To answer these we need an out-of-ecliptic view on the Sun.

More practical reasons to answer these questions:

1. Maunder minimum happened. Will we be able to predict the next Maunder minimum? Needpole observations.
2. The number of payloads launched per year has gone from 100 to 2500 from 2015 to 2025. By 2035 the space economy is projected to reach 1.8 trillion. 
3. May 2024 superstorms caused large disturbances to magnetosphere. What will be the effect from even larger storms?

Problems that the budget is flare not allowing us to do new things. However we have to think beyond it. We could fly missions to poles that are cheaper than HELEX.

2. Panel Member: Don Hassler: SOLARIS;

Solar Polar Imaging Mission has been a long-time discussion;

Heliophysics MIDEX Phase A Study (2019-2021): $250M budget (much less than Solar Polar HELEX-class mission for $500-750M).

Key priorities of the decadal survey solar polar mission:

1. Obtain clues to the mechanism of solar dynamo (polar magnetic fields, flows)
2. Space weather;
3. How do CMEs interact with the corona and evolve in longitude;

Key instruments:

1. Imaging: Doppler, Magnetogram, EUZV images, White-light coronograph;
2. In-situ: Magnetometer, Ion -electron spectrometer, composition;

A solar orbiter mission is an opportunity the community has bee waiting for 50 years; we could do it within the budget;

3. Panel Member: Samantha Wallace: improving coronal modeling and solar wind predictions with a future solar polar mission;

Problem: polar photospheric field is needed for extrapolations but we have never observed these at 90 degrees; Typically all we have are carrington rotation maps plus flux transport models (e.g. ADAPT, AFT, SFT) that allow us to go from asynchronous to synchronic maps;

Key discoveries enabled by polar measurements of B:

1. The global solar magnetic topology: the strength, structure and distribution of the polar field;
2. Full description of differential and meridional circulation;
3. All of the above is needed for space weather.
4. New directions!

In a recent study Wallace has shown that inclusion of far-side information from Solar Orbiter leads to much precise capturing of e.g. CME prediction.

4. Panel Member: Robert Allen: synergies between Solar Polar and Solar Orbiters.

1. How can we best leverage Solar Orbiter off-ecliptic observations to refine Solar Polar Orbiter science objectives?
2. How do you convey to the public that solar polar mission and science is cool? This would help us to convince congress in the future.

Questions/Discussion:

• Gombosi: How can we launch things safely if SpaceX has a hard time getting to altitudes above 0?
• Don Hassler: without relying on Falcon 9 but by using Starship. We need smaller missions to lead to large ones (e.g. IBEX -> IMAP, TRACE -> SDO).

• DeNolfo: China is interested in polar missions. What do we do with it?
• Don Hassler: November 2024: Chinese workshop for solar polar mission. Unclear if the US will collaborate; Also this pushed the US to move to the poles.

• KD Leka: can we coordinate Polar Solar Orbiter mission with Solar orbiter to observe several poles at once or from different vantage point to maximize the scientific return;
• Don Hassler and Nour: There are already instruments planned for different vantage points, e.g. Vigil: L5, Koreans: L4; what we need is a new polar-like mission at a smaller budget to convince the community;

• Sue Lepri: could we attract private funders from PSO?
• Nour: lately NASA and Congress has been very keen in supporting space weather; private sector: not sure; we could try it in the future;
  • Q: How about Elon Musk?
  • A: He is interested in Mars; We are interested in the poles;

• How could we convince NASA that poles are cool?
• Don: There is science fiction. Also working with the sponsor and trying to convince them that we could do it on the budget.
• Nour: Convince your congress members; We need support from the SMD (Science Mission Directorate).

—————

Organizers: please think what a solar polar orbiter should be: key components:

1. Samantha: Photospheric field measurements; flows;
2. Robert Allen: Look at the whole pole view (logitudinal view) to see long-term evolution of poles
3. Don: community is ready for this mission; Helioseismic community, CME community are ready.
4. Nour: room for discovery is huge; opportunity is there (could do it on the budget) which is also a challenge. These 3 are a recipe for success.

Additional Notes

Discussion led by Erika Palmerio; note taker: Brian T. Welsch

SQ = Speaker Question

SC = Speaker Comment

AS = Audience Suggestion

AQ = Audience Question

AC = Audience Comment

Useful links: (1) NASA proposal selection statistics from sara.nasa.gov; (2) NASA’s website to volunteer for panels, for grad students or post-docs who want to serve on review panels as Executive Secretaries;

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SC: NASA’s LWS Focused Science Topic program supports multiple teams

(that propose separately) to address specified research questions.

(Unlike NASA’s Heliophysics Guest Investigators or Heliophysics

Supporting Research programs, in which proposers are free to identify

questions they feel are most important.

SC: We need to generate some suggestsions for FSTs — if we don’t, the

topics adopted might not be to our liking.

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AS: We should have a topic on CMEs generally

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AQ: What are success rates?  Is there an effort to maximize submissions?

            SC: I do not know this info.

            AC: NASA tracks success rates, which is publicly available, at:

https://science.nasa.gov/researchers/sara/grant-stats

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AQ: For people in this room, how should one go about submitting a topic?

            SC: There is a Google Doc to be filled out.  I suggest working

            with a group, to sharpen ideas.

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AQ: If there is no LWS call for proposals this year, will topics be carried forward?

            SC: Existing proposed topics that might be brought forward:

            * Physical Processes Responsible for the Generation & Evolution of

            the Solar Wind

            * Solar Flare Energetic Particles & Their Effects in Large Solar

            Energetic Particle Events

            * Improve Probabilistic Forecasting & PHysical Understanding of

            Extreme Solar Events and their Impact on Heliosphere & Terrestrial

            Magnetosphere

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AQ: Is there a need for the topic to involve (or proposals) to include

satellite data.

            SC: You can propose to use ground based data.

            AC: You should include *some* NASA satellite data.

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AQ: Are Strategic Capabilities or Tools & Methods reviewed by LPAG?

            SC: No, LPAG does not review these.

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AC: For those thinking of proposing, esp. more junior scientists or

grad students, you must identify *specific* questions, perhaps

identifying *specific hypotheses* that can be tested with available

observations.  Questions to be addressed need to be important, but we

MUST also be able to make progress in addressing them.

Grad students and post-docs should consider volunteering for a NASA

panel as an “Executive Secretary” (not a reviewer, but you observe the

review process).  Students can ask their advisor to email NASA program

officers to suggest their names, and students and post-docs can

volunteer directly at:

https://science.nasa.gov/researchers/volunteer-review-panels

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AC: The topics proposed must be “sharp” enough for work done in 3-4

years to make substantial progress.  It is important to have a

well-defined GOAL.  (This is relevant for the question about “measures

of success” on the Google Doc.)

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AQ: How much of LWS will address Machine Learning and Artificial

Intelligence?

            SC: These should be tools to address questions, but not a

            focus of the effort itself.

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AC: Space Weather is currently an important motivating factor at NASA.

Thus, it is probably best to frame proposed science topics in terms of

Space Weather.

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AC: With less funding available, there will either be fewer topics, or

fewer teams per topic, or less money per team,

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