SHINE 2026 Sessions and Summary Reports

William Ashfield: Southwest Research Institute (SwRI), Ryan French: Laboratory for Atmospheric and Space Physics (LASP) and Juraj Lorincik: Bay Area Environmental Institute (BAERI)

Scene Setters: Marcel Corchado-Albelo: University of Colorado Boulder (CU); Matthias Rempel: High Altitude Observatory (HAO)

The CSHKP model of solar flares, published between 1964 and 1976, turns 50 years old this year. Serving as the organizing framework for solar flare phenomena during this time, the standard model is inherently limited: restricted to two dimensions and built on a set of implicit axioms ‚   symmetric energy deposition, planar current sheet geometry, eruptive flux rope‚  that are treated as universal. However, recent observations increasingly reveal flare behavior that violates the standard model, including the absence of null-points, multi-ribbon topologies, non-eruptive sheared arcades, persistent footpoint asymmetries, and fine-scale structure that highlights the intrinsic 3D nature of these events. 

This session asks what the next-generation ‚ standard flare model should look like, with an emphasis on 3D magnetic structure and energy release. Central to this is identifying which phenomena are truly universal (reconnection as the energy release mechanism, ribbons as maps of that process) and which have been over-generalized (symmetric energy input, 2D current sheet geometry, eruptive behavior). We invite contributions that test these axioms observationally, confront models with the full diversity of flare phenomena, and identify the measurements still needed to build a more complete 3D framework.

1. What physical properties are universal to all flares, and which reflect specific magnetic configurations or event types?
2. What recent evidence points to the nature of 3D reconnection and energy release processes in flares?
3. What future observations are needed to validate or discriminate between candidate flare model frameworks?

Session Summary

This session marked the 50th anniversary of the CSHKP standard flare model and asked how the community can move toward a next-generation, fully 3D picture of solar flares. Talks and discussions spanned observational 3D flare morphologies, the diversity of MHD models, and the question of how different event types can fit within a generalized framework.

Rather than treating CSHKP as a single monolithic cartoon, the session framed the standard model as a flexible toolkit whose components can be applied selectively depending on the flare morphology and observations at hand. The consensus was that we, as a field, currently bring different lenses to how we use the standard flare model as a tool, and to make sense of a given flare, we apply certain parts in the absence of others.

A central conceptual question arose in our conversation: Is there a single standard model, or many? The consensus leaned toward a generalized model built from shared axioms, anchored from the current sheet, from which the community selects the relevant components for a given event. This reframing can directly address how confined flares and failed eruptions integrate into CSHKP (whether confined flares are simply failed eruptions, or reflect topologies that fundamentally inhibit CMEs), how onset and rising flux ropes fit in, and whether nanoflares force us to redefine what a flare is; i.e., whether a flare is fundamentally just energy release via magnetic reconnection. It was also noted that the historical model itself has evolved (e.g., Kopp & Pneuman 1976 did not include eruptive flux ropes), underscoring that CSHKP has always been a living framework.

The current sheet was identified as the most fundamental model component, and much of the discussion centered on the magnetic topologies that give rise to it. Breakout reconnection at null points was examined across different cases, with null-point heights, strapping-field strengths, and eruptive classes all shown to matter. Stronger overlying fields inhibit eruption and alter the reconnection dynamics. This raised the question of how to locate null points from the magnetic field, and whether such a structure could be identified through differential observations. Complementary modeling showed that 3D field extrapolations can produce current sheets, providing a natural connection to observed hot-ridge features. The session also considered the importance of reconnection at magnetic separators and the distinction between quasi-separatrix layers (QSLs) and true separatrix layers (SLs), asking whether it actually matters, physically, if the current sheet originates from a QSL or an SL.

The flux rope emerged as a key locus of energy and connectivity. Microwave and X-ray observations provide evidence for electron deposition at the bases of the flux rope, implying that large amounts of thermal and non-thermal energy reside in the upper corona (within the flux rope) that may not be accounted for in standard flare energy budgets. This motivated discussion of the magnetic connectivity threading from the current sheet, through the flux rope, and out to the remote ribbons, and of the fact that FASR (microwaves) and FOXSI-S (X-rays) will have sufficient dynamic range to detect low- and upper-altitude sources simultaneously. On the modeling side, further simulations of flare confinement, showing how flux ropes can reconnect with overlying structures to prevent eruption, and prompting broader questions about when the “pre-flare” phase truly begins and what that implies for the requirements of simulating flares.

Scientifically, the session pointed toward developing a generalized standard flare model expressed as a set of shared axioms that can explain multiple morphological components simultaneously, explicitly incorporating confined flares, failed eruptions, and potentially nanoflare-scale events. This raises the broader task of arriving at a working definition of a flare that holds across spatial scales. Fundamentally, a flare is simply a release of energy via magnetic reconnection. Priorities include reconciling how SADs and other loop-top dynamics appear across MHD simulations versus other model frameworks, better accounting for thermal and non-thermal energy in the upper corona and flux rope within flare energy budgets, and clarifying the role of the pre-flare chromosphere in shaping ribbon structure.

Present-day 3D MHD models replicate combinations of eruptive and non-eruptive flares, along with many of the observational features discussed throughout the session — remote ribbons, QPPs, and SADs. They continue to struggle, however, with reproducing flare timescales and tend to overestimate transition-region emission. As a group, we identified the need for greater physical sophistication and numerical realism in 3D MHD simulations, and for using multiple models collectively to span the full range of spatial scales.

Practically, upcoming and next-generation instrumentation featured prominently: FASR and FOXSI-S for simultaneous multi-altitude microwave/X-ray diagnostics, and coordinated DKIST flare campaigns (a DKIST flare-month effort was raised). A specific observational goal is to directly locate null points in the magnetic field to test breakout and CME model predictions, potentially via differential measurements or linear polarization diagnostics. These will help test model predictions about magnetic connectivity from the current sheet through the flux rope out to remote ribbons. Continued sessions building on this 50th-anniversary framing would be valuable for consolidating the community’s many “standard models” toward a coherent, generalized picture.

Elizabeth Wraback (HAO/NSF NCAR), Samaiyah Farid (Alabama A&M University)

Scene Setters: Dr. Urszula Bąk-Stęślicka, (Astronomical Institute, University of Wroclaw) Dr. Yuhong Fan (High Altitude Observatory, NSF-NCAR)

Coronal cavities are density-depleted regions in the solar atmosphere surrounding prominences. These structures can last entire solar cycles, never erupting, or erupt into CMEs, making them important CME precursors. Spectropolarimetric observations by CoMP/UCoMP have shed insight into the magnetic structure and, when combined with forward modeling, suggest the pre-eruptive structure of the CME is a flux rope. However, limited observations do not allow us to fully discriminate between flux rope and sheared arcade, leading to the need for future observatories, like COSMO, and combined modeling efforts.

What can coronal cavities and their current observations tell us about the initial magnetic structure of eruptions?

What makes coronal cavities quiescent versus eruptive? 

What observations are needed to discriminate between different magnetic field structures?

Session Summary

This session focused on understanding the formation, and pre-eruptive structure of coronal cavities.

Part 1: Observations of Coronal Cavities

The first section focused on , first, introducing and explaining coronal cavities and, second, discussing multiwavelength coronal cavity observations.The audience discussed several clarifying questions on whether active-region and quiet-Sun cavities are physically distinct or whether they reflect the same basic magnetic structure in different environments. While quiet-Sun cavities tend to be larger and longer-lived, and active-region cavities may be lower and more compact, both likely involve sheared or twisted magnetic fields and prominence material. It is not clear if AR cavities have different temperature distributions before/after CME eruptions.
Additional discussions clarified the impact of projection and instrument sensitivity on cavity/CME relationships. Not all CMEs show obvious pre-existing cavities, but many eruptions likely involve cavity-like magnetic structures that may be faint, low-lying, or hidden by projection.

A major theme was the difficulty of distinguishing flux rope and sheared-arcade models via observations. The concentric Doppler velocities and lagomorphic “bunny ear” signatures are suggestive of flux-rope structure, but they do not fully rule out sheared arcades. The cavity core is the most important region for discriminating between models, especially with circular polarization measurements that can better constrain the line-of-sight magnetic field. The session also highlighted the need for more realistic models that include heating, turbulence, Alfvén-wave processes, density structure, plasma drainage, and possible partial eruptions or outflows along the cavity. Density fluctuations may help distinguish coherent flux-rope geometry from more chaotic sheared-arcade configurations, but density alone is not a clean diagnostic. Distinguishing models will require spectropolarimetry to deduce the full magnetic field.

Part 2 : Current State of Cavity Models

The modeling discussion centered on the ability to reproduce key components of coronal cavities: flux-rope, hot-nugget features of the Gibson-Low cavity model and Doppler red/blue signals that show concentric/nested circles of alternating flows. Through audience discussion, it was noted that distinguishing the flux-rope formation method (sheared vs tether cutting) is difficult because different models can produce very similar observable signatures. In particular, a strongly sheared arcade and a flux rope with roughly 1.5 turns may appear nearly indistinguishable in both observations and forward models. Doppler observations are also helpful in determining the handedness of the filament, which could help constrain models of particular events.

Models of polar crown filaments using RBSL technique (presented by Arpita Roddanavar -NJIT ) show that multiple filaments can be important in the eruption. Results indicate that one filament brightened, while another was responsible for releasing material, therefore complex dynamics could be involved with each eruption.
Current models cavity/CME models still have many limitations. Many models (PINN, PHASER) use LOS magnetograms from the photosphere to reproduce cavities. But these are not force-free so they are not a full reflection of the magnetic topology. It was noted that PIN models do not require force-free but J. Linker presented the caveat that Yes, PIN models recreate corona but that is because currents produced in the corona are imprinted on the linear magnetic field in the photosphere so then you can get info, but you cannot distinguish between coronal and photospheric magnetic field. B.Chen noted that radio observations may offer direct measurements of magnetic fields. Preliminary results of Bfield of ARs can distinguish thermal and non-thermal emission and spatially pinpoint source regions.

Progress in the three main questions of this session relies on 1) improved direct measurements of the magnetic field of coronal cavities, in particular the inner region known as the chewy nugget. DKIST Spectropolarimetric observations show promise in this area, but long integration times and data limitations provide additional challenges. Future observations will provide a larger dataset and could help discriminate models. Radio observations could also provide some insight through future collaborations. 2) More comprehensive cavity models that include mass loading/drainage,heating, turbulence, Alfvén-wave processes, density structure, and complex scenarios involving multiple filaments could better determine the trigger of cavity eruptions. 3) Theoretical models that can identify distinguishing features and expected observations between flux-rope, sheared arcade model are essential. 4) Future facilities such as COSMO will be critical for expanding spectropolarimetric coverage of the corona and providing the observations needed to connect cavity structure, magnetic topology, and CME initiation.

Cecilia Mac Cormack (1,2), Abril Sahade(1) — 1- Heliophysics Science Division, NASA Goddard Space Flight Center, MD, USA — 2- The Catholic University of America, DC, USA

Scene Setting Speakers: Phil Hess (NRL) – Erika Palmerio (PSI)

Solar eruptions release large amounts of solar plasma and more intense magnetic fields into the interplanetary medium than the surrounding environment. They are observed across multiple stages: in the lower corona as flares and/or prominence eruptions, in the upper corona as coronal mass ejections (CMEs) in white-light images, and later through in-situ measurements that detect the arrival of the associated magnetic flux rope at a spacecraft. Despite these diverse observations, the  hidden region  in which CMEs evolve from structured solar eruptions into large-scale interplanetary transients interacting with the solar wind remains poorly observed. This missing link continues to limit our ability to connect remote and in-situ signatures into a unified physical picture of the CME life cycle.

In this new era of solar observatories (e.g. Solar Orbiter, Parker Solar Probe, PUNCH), we count with more information than ever to increase our understanding of the evolutionary process of CMEs. To understand the complete evolution of the CMEs 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, their internal structure and interaction with the solar wind.

How is the life story of a CME in the observationally  hidden region?
 
Which tools do we currently use to bridge that gap? 
 
How the new observations (remote and in situ) of the inner heliosphere and/or models can leverage our understanding of the CME life story?

Session Summary

The session focused on the observational gaps that define the “hidden region” of CME evolution and how models can fill that gap. The discussion was highly productive and covered many important aspects.

We highlight a few key points here:

From observational POV:
-The community agrees that CME behavior beyond the low corona is still poorly constrained, and that CME deceleration and solar wind-CME or CME-CME interactions continue developing in the hidden region, showing that the dynamical evolution of a CME is far from settled once the initial acceleration phase ends.
-It was also highlighted that features within a single CME are not that simple to identify as they can move at different speeds, and they are not necessarily located at a single position along the line of sight, which complicates interpretation under the Thomson sphere assumption. Related to this, CME duration remains difficult to define objectively since different catalogs disagree on how to identify the “end” of a CME in the data, pointing to a need for more consistent, physically motivated criteria.
-On the in-situ side, the session highlighted a fundamental limitation: a single-point measurement along one spacecraft trajectory tells us very little about a CME’s global 3D structure, and multi-spacecraft measurements within the same ICME are needed to make progress here. However, funding constraints make it unlikely that new missions will provide fundamentally new vantage points in the near term, which shifts emphasis toward better exploitation of existing datasets, much of which merits further or renewed analysis.

From the modeling side:
-The community agrees that key properties of a CME at 1 au can be highly sensitive to small variations in initial conditions, meaning better tools need to be developed in order to trustfully track CMEs.
-The discussion turned to how well current MHD models of CME eruption and propagation reproduce observations. While these models often capture key aspects of real events, agreement is typically assessed qualitatively, raising the question of whether more precise, quantitative agreement metrics are achievable. This also raised the question of how many subjective choices, such as model parameters or the selection of field lines to integrate, shape the resemblance between simulations and observations, and to what extent these choices are effectively being tuned to match the data rather than derived independently.
-At the same time, it was emphasized that current MHD models incorporate substantial physics (e.g., inner boundary conditions, parametrized solar wind heating), linking core model components directly to observations, and that current qualitative agreement represents a genuine and remarkable improvement over past decades.

Outlook for scientific and practical developments, including future research directions and session topics:
The session raised an open question about what the next major addition to CME modeling should be. Options discussed included ingesting additional observational data beyond magnetogram maps. For example, using coronagraph observations to update models of an eruption already in progress, and adapting data assimilation techniques from terrestrial weather forecasting to heliophysics.
More broadly, the group agreed that progress on the “hidden region” of CME evolution will require combining underused existing data with better multi-spacecraft in-situ coverage, more objective and quantitative model-observation comparison metrics, and modernized propagation/initiation models that account for internal CME structural evolution rather than relying primarily on new missions, which are unlikely given current funding realities.

Future Sessions:
Building on this year’s discussion, a follow-on topic would be “Quantifying Agreement Between CME Models and Observations,” focused on developing objective metrics to assess model performance and disentangle genuine physical agreement from parameter tuning.

Shea Hess Webber (Stanford), Krishnendu Mandal (NJIT), Oana Vesa (Stanford)

Understanding the global magnetic field is key to enhancing heliospheric models, and accurate forecasting and prediction of space weather. The solar dynamo generates, stores, emerges and transports the solar magnetic field, but the mechanisms governing these processes are not fully understood. Because the surface is the inner boundary for the rest of the heliophysics field, this incomplete understanding impedes modeling and forecasting efforts. Without clarifying the dynamo process, progress towards more accurate coronal and solar wind modeling, and space weather forecasting at Earth, the Moon, Mars and beyond, will remain constrained. We aim to foster discussion that connects different physical processes, incorporates ideas from the solar magnetism “user community,” and considers downwind impacts.

1) What are the key mechanisms for emerging flux from the deep interior to the surface, both at the local and global scale?

2) How do convection, turbulence, and atmospheric dynamics affect flux emergence, transport, and diffusion?

3) What are feasible timescales of prediction of emergence?

Bin Chen (New Jersey Institute of Technology), Peijin Zhang (New Jersey Institute of Technology), Sam Schonfeld (  Air Force Research Laboratory)

Scene Setters: Peijin Zhang (New Jersey Institute of Technology), Lindsay Glesener (University of Minnesota)

The next decade will see the rise of “Large-N” radio interferometers—arrays featuring a large number of antennas—including the operational OVRO-LWA, MWA, and LOFAR, alongside the highly anticipated next-generation solar radio telescope Frequency Agile Solar Radiotelescope (FASR), and the general-purpose Square Kilometre Array (SKA) and Next-Generation Very Large Array (ngVLA). While these observatories will offer unprecedented imaging fidelity, dynamic range, and resolution, their greatest impact on the SHINE community may be a shift in accessibility.

In the past, using radio data required highly specialized interferometry expertise and months of processing raw visibility datasets one at a time. That era may be ending. To handle large data volumes, fully automated calibration and imaging pipelines are required to process the raw data and produce science-ready, radio spectropolarimetric image “hypercubes.” The primary goal of this interactive session is to explore how to prepare for this new era. We encourage the sharing of success stories, as well as challenges and caveats, when producing and utilizing these data products for science. We will also brainstorm ways to help non-radio experts seamlessly integrate radio observations into their research.

1. How will the shift from raw visibility processing to directly analyzing the multi-dimensional radio image products transform the broader SHINE community’s approach to heliophysics and space weather research?

2. What physical constraints can non-radio experts extract from the current and future radio datasets to advance their distinct science questions?

3. What tools or training resources (including AI) does the community need to ensure these radio products are truly accessible and useful to researchers without much background in radio interferometry?

Session Summary

The SHINE 2026 Era of Large-N Radio Arrays session highlighted the growing importance of radio observations for understanding the solar atmosphere and heliosphere. Radio measurements uniquely probe energetic particles, magnetic fields, plasma density, and emission processes across atmospheric layers that are difficult to access with optical, EUV, or X-ray observations. Discussions focused on recent scientific progress, major challenges, and future opportunities enabled by next-generation facilities and advanced computation.

A major theme was the transition into the “large-N era” of solar radio interferometry, where N denotes the number of antennas. Facilities such as Owens Valley Radio Observatory Long Wavelength Array, Expanded Owens Valley Solar Array, and Low Frequency Array have demonstrated that increasing antenna count substantially improves imaging fidelity, enabling imaging spectroscopy of fine coronal structures such as loops, CME-driven shocks, and radio burst source regions. Radio diagnostics are increasingly used to infer physical parameters, including electron density, temperature, magnetic field strength, and energetic electron distributions. Type II bursts remain important probes of CME-driven shocks, while Type III bursts trace electron escape into the heliosphere and offer valuable context for solar energetic particle (SEP) forecasting. Forward modeling and data-driven approaches are also improving the translation from radio observables to physically meaningful parameters.

Several challenges remain. Interpreting radio observations is often model-dependent because multiple emission mechanisms can coexist in the same event. Disentangling these sources requires spectral decomposition and will be greatly facilitated by large-N observatories, which offer improved spatial resolution and greater dynamic range, enabling investigation of both smaller and fainter sources. However, coronal scattering, refraction, and the optically thin nature of much of the radio emission blur intrinsic source structures, imposing practical limits on achievable resolution. This sets a (frequency-dependent) upper limit on the useful maximum baselines of radio arrays, which should be considered during their design.

Data volume presents another major challenge. Large-N observatories generate data at rates reaching tens of terabytes per day, making long-term storage of raw visibilities impractical. The community expressed strong interest in calibrated image products and in applying their own processing to generate higher-level physics products, highlighting the need for scalable data services that balance accessibility with scientific flexibility. No major concern was expressed by the inability to archive all of the raw visibilities used to generate the calibrated images.

Upcoming facilities promise major advances. The Frequency Agile Solar Radiotelescope remains a high-priority future observatory that will greatly improve sensitivity, resolution, spectral coverage, and polarization capability. The Solar Submillimeter Array will open a new submillimeter window on chromospheric and flare physics, while SunRISE will extend spatially resolved radio observations into low frequencies inaccessible from the ground, enabling studies of radio bursts throughout the inner heliosphere.

There was an important discussion about the potential for Type III radio bursts to inform SEP (especially protons) forecasting. Type III bursts indicate (at the speed of light) accelerated electrons associated with accelerated protons that arrive as SEPs in the heliosphere minutes to hours later. Monitoring the position of Type III bursts simultaneously from Earth and L4, combined with solar wind footpoint mapping, would be extremely valuable for initiating alerts to astronauts (both at Earth and in transit to and from Mars) about potentially dangerous SEP events before they arrive.

Machine learning also represents a promising frontier, with potential applications in calibration, image reconstruction, event classification, and physical inversion. These applications should be explored and tested to facilitate the transition to large-N solar arrays. Additional particularly valuable future research directions include integrating radio observations with multi-wavelength data and physics-based models to improve understanding of CME evolution, shock acceleration, and SEP production.

Arpit Kumar Shrivastav (Southwest Research Institute), Yeimy Rivera (CfA | Harvard & Smithsonian), Prateek Mayank (University of Colorado, Boulder)

Scene Setters: Samantha Wallace (Embry-Riddle Aeronautical University) and Emily Mason (Predictive Science, Inc.)

The solar wind is a fundamental component of the heliosphere, yet quantifying how contributions from different source regions collectively determine its global properties remains a major challenge. The unprecedented proximity of Parker Solar Probe and the multi-instrument capabilities of Solar Orbiter allow us to observe the transition from a structured corona to a dynamic heliosphere. Despite this progress, linking coronal processes to their in-situ signatures remains a difficult task, thus limiting our understanding of solar wind origin. This session aims to explore the solar wind as a multi-source, global phenomenon that demands robust magnetic connectivity between remote sensing and in-situ observations and improved numerical modeling for a comprehensive understanding.

1. What is the relative contribution of different source regions to the global solar wind and their associated processes?
 
2. What are the fundamental physical and technical limitations that prevent robust magnetic connectivity between remote-sensing and in-situ observations?
 
3. How can we better utilize in-situ and remote sensing observations to improve numerical models to reproduce the observed global evolution of the solar wind?

Session Summary

This session investigates the coupling between the solar atmosphere and the heliosphere by exploring the multi-source origins of the solar wind within a global magnetic context. A primary objective is to understand the relative contributions and underlying processes of various slow solar wind sources. Furthermore, the session also aims to discuss the current limitations in connecting remote-sensing coronal observations with in-situ heliospheric measurements. To advance the community toward a unified understanding of the integrated Sun-to-heliosphere system, this session brings together observers and numerical modelers to address key bottlenecks in data analysis, composition measurements, and global magnetic field modeling.

The session generated extensive multi-disciplinary debate around three major questions which are essential for current solar wind research: how the wind originates and accelerates, where global connectivity modeling breaks down, and how multi-instrument composition diagnostics can be used efficiently.

A. Solar Wind Origin, Release, and Acceleration: A major theme of the discussion was the need to move beyond the traditional view that relates the solar wind observed at 1 AU to a single source region. Instead, everyone emphasized and agreed treating the problem through four interconnected aspects: origin (the magnetic topology in the solar atmosphere), release (the processes that allow plasma to escape), acceleration (energization through waves, turbulence, and other mechanisms), and propagation through the heliosphere. Within this framework, the Separatrix Web (S-Web) and pseudostreamer models were highlighted as important extensions to the classical interchange reconnection scenario. The scene-setting speaker discussed the Squashing-factor maps that show that reconnection preferentially occurs along complex networks of separatrices and quasi-separatrix layers, providing a natural explanation for why the slow wind source region extends well beyond the heliospheric current sheet. Long-term studies also suggest that active region peripheries can contribute a substantial fraction (30–80%) of the open magnetic flux during solar maximum, while their contribution is negligible during solar minimum. However, it was emphasized that identifying open magnetic flux alone does not confirm plasma release, and direct observational evidence is still required to establish the connection between magnetic topology and the solar wind.

B. Limitations and Uncertainties in magnetic connectivity: A major focus of the discussion was the uncertainty associated with magnetic connectivity. One of the key challenges is the lack of continuous 360° measurements of the photospheric magnetic field. As a result, time-dependent models must introduce far-side active regions only after they rotate onto the visible disk, leading to artificial changes in the heliospheric current sheet and making it difficult to distinguish real temporal evolution from modeling artifacts. Additional sources of uncertainty arise from the limited spatial resolution of global models (typically 1–2°), the evolution of the supergranular magnetic network, systematic differences between magnetograms from GONG and HMI, line-of-sight to radial field corrections, errors introduced by simple ballistic propagation and sudden changes in the global magnetic topology due to eruptions. Combined, these effects can produce uncertainties of 6–24 hours in magnetic connectivity, highlighting one of the major limitations in reliably linking coronal source regions to in-situ solar wind observations.

C. Connecting sources through composition measurements: Another major topic was the use of plasma composition as a diagnostic of solar wind origin. Elemental abundance ratios, such as Fe/O, are determined by First Ionization Potential (FIP) fractionation in the chromosphere, whereas charge-state ratios, such as O7+/O6+, are established higher in the low corona. Therefore, a strong correlation between these quantities is expected for steadily expanding open magnetic flux, while a clear decoupling can indicate plasma released through interchange reconnection. Furthermore, recent coordinated observations from Solar Orbiter (HIS and SPICE) together with near-Earth measurements from ACE and Wind have shown that mesoscale variations in plasma composition and structure can remain preserved during propagation to about 1 AU under favorable magnetic connectivity. These results provide an important opportunity to directly compare remote-sensing observations with in-situ measurements and test models of solar wind origin.

The discussion concluded by identifying several priorities that could significantly improve our ability to connect the solar atmosphere with the heliosphere and better understand the origin of the solar wind.

1. A key priority is the development of standardized uncertainty estimates for magnetic connectivity. Future studies should quantify the uncertainties associated with magnetic back-mapping, including errors arising from different sources.
2. Another important direction is the implementation of systematic, coordinated observing campaigns. A proposed strategy is to first identify time intervals which are not affected by ICMEs and shocks, perform retrospective WSA/ADAPT modeling that accounts for previously unseen far-side magnetic flux, and directly compare the mapped footpoints with high-resolution S-Web (Q) maps and FIP-bias observations from SPICE and EIS.
3. The session also highlighted the need for improved observational capabilities. While increasing the resolution of numerical models remains important, overcoming current connectivity limitations will require new observations. High-priority requirements include continuous magnetic field measurements from off-Sun–Earth-line vantage points such as L4/L5, high-latitude magnetograms to better constrain the global magnetic field, and direct measurements of the coronal magnetic field.
4. Finally, given the strong interest and active discussions on magnetic connectivity, magnetogram calibration, surface flux transport, and plasma release mechanisms, participants suggested organizing a follow-up SHINE session dedicated to discuss the several aspects of solar wind observations and modelling. Such a session would provide an opportunity to evaluate current approaches and identify the key developments needed for more reliable Sun-to-heliosphere connectivity studies.

Christina Kay (JHU APL), Erika Palmerio (PSI), Robin Colaninno (NRL), Teresa Nieves-Chinchilla (GSFC)

The corona and heliosphere form a coupled, interconnected system with a dynamic transition region between them, yet they have historically been studied as distinct domains. Solar Cycle 25 has ushered in a new generation of heliophysics missions—including Parker Solar Probe, Solar Orbiter, PROBA-3, and PUNCH—that, together with well-established observations from near 1 au, are overcoming these limitations. This synergy of observations provides unprecedented perspectives on both the large-scale structure and transient phenomena of the solar wind, including the critical coronal–heliospheric transition region. In particular, these datasets are advancing our understanding of coronal mass ejections (CMEs) and their evolution, while also revealing new complexities in the corona–heliosphere connection. This session focuses on integrating observations and models to explore the coupled corona–heliosphere system, identify remaining knowledge gaps, and highlight emerging insights as well as exciting unknowns in our understanding of the Sun’s dynamic environment.

Sue Lepri (University of Michigan), Jackson MacTaggart (University of Michigan), and Liang Zhao (University of Michigan)

Scene Setting Speakers: Len Fisk (Theoretical model, UMich), Jackson MacTaggart, Liang Zhao (observations, Umich) and Tamar Ervin (UC berkeley, PSP observations, but didn’t present due to limited time)

The previous understanding, based on observations from Ulysses and ACE in the past decades, indicates that the total open magnetic flux of the Sun outside the streamer-belt region remains constant across multiple solar minimum conditions. The total open magnetic flux is defined as the product of BrR^2 and the solid angle occupied by open-flux regions outside the HCS‚  streamer belt. One of the implications of this conservation is that  the variations in BrR^2 arise from changes in the solid angle of the region outside the streamer belt, or equivalently, from variations in the width of the HCS‚  streamer region.
 
At heliocentric distances far from the tips of the HCS‚  streamer loops, the solid angle of the region outside the streamer belt is nearly constant. As a result, BrR^2 is expected to remain approximately a constant value, as observed at 1 AU. This constant is 3.67 (nT AU^2) as given by Ulysses and ACE observations. Recent PSP/FIELDS observations (results provided by S. D. Bale), however, reveal that when the heliocentric distance is less than about 0.2 AU, BrR^2 outside the HCS‚  streamer regions is reduced by about 20% from this constant value as at 1 AU. These findings suggest that open magnetic flux measurements from PSP encounters may have important implications for estimating the width of the HCS‚  streamer belt. More broadly, investigations of the Sun‚  open magnetic flux at different heliocentric distances can provide critical insights into the evolution of solar magnetic fields and improve our understanding and prediction of solar cycle variability.

1.   What global physical processes on the Sun is governed by the behavior of the magnetic open flux

2.  How can we use the magnetic field measurements from the PSP encounters to interpret the topology of the HCS-streamer belt?

3.  Based on the solar wind and magnetic field observations we have for the recent solar cycles, what can we do to interpret and predict the solar cycles?

Session Summary

Len Fisk presented his model for the evolution of the global magnetic field over the solar cycle, and the ability to predict the strength and length of the next sunspot cycle based on the observations of open magnetic field and angular extent of the helmet streamers. The basis for this mode is that the Sun has a fixed internal dipole field, tilted by 10 degrees; and a surface layer with network lanes surrounding supergranules that is highly magnetically permeable and separates the fixed dipole magnetic field from the open magnetic field. Loops that arise from the fixed dipole interact with the open flux to create sunspots and then ultimately destroy sunspots and reform the poloidal magnetic field with an opposite polarity to end the cycle. During this process, one main current sheet rotates over the poles of the Sun before returning to the equator. The minimum value of the open magnetic flux at solar minimum is found to be constant and equal to 5.1e22Mx. This model predicts the next sunspot cycle (Cycle 26) will last 11.6 years and have a max of 222 sunspots. This model contrasts the standard solar dynamo model which originates deep below the surface of the Sun.

Liang Zhao showed the comparison of the model predicted solar maximum sunspot number with the observations of monthly sunspot number. For the recent five solar cycles (Cycles 21-25), the model’s predictions match with observations very well.

Jackson MacTaggart discussed the approach to use PSP encounter 12 observation of Br to derive the 27 degrees width of the streamer belt that could be the width in the Cycle 26 minimum, which also agrees well with the model prediction.

Discussions focused on some of the assumptions of the model. Such as:

1. Observations of more than one current sheet in the heliosphere and how that observation affects this model–the answer is it doesn’t since this is a global model
2. The role of the internal dipole field and the generation of bipoles that move in network lanes and ultimately are destroyed to reform the poloidal magnetic field.
3. The difference between this model and the standard dynamo model, and how this model does not require the internal dipole to convert one polarity of flux into another.

On the scientific side, an important direction is to continue validating and refining the model using upcoming observations from Parker Solar Probe and Solar Orbiter, together with historical sunspot records from the past ~250 years. These efforts would help assess the model’s performance across multiple solar cycles, support further theoretical refinement, and emphasize the important role that the Sun’s open magnetic field plays in driving the solar cycle.

On the practical side, future work could explore the utility of the model’s predictive capabilities, particularly for applications such as space-weather forecasting and planning future observations or missions. Potential future SHINE sessions could be proposed to provide a platform for discussion and collaboration among theorists, modelers, and observers, with the goal of further testing, refining, and applying this model—or related models that identify the Sun’s open magnetic flux as a primary driver of the solar cycle.

Nishtha Sachdeva (Univ. of Michigan) Prateek Mayank (SWx TREC Univ. of Colorado) Dinesha Hegde (Univ. of Alabama in Huntsville)

Scene Setters: Carlos Braga (JHU/APL), Abril Sahade (NASA/GSFC)

Extreme space weather events such as unusually strong geomagnetic storms are often driven not by isolated coronal mass ejections (CMEs), but by sequences of eruptions whose interactions amplify their heliospheric and geoeffective consequences. Despite recent progress, identifying reliable observational signatures of such extreme, multi-CME events remains challenging due to projection effects, limited coronal and heliospheric coverage, and ambiguities in associating solar sources with in-situ impacts. Building on the SHINE 2025 session on interacting CMEs, this session aims to streamline the discussion by focusing on two key aspects: (1) observational identifiers of extreme CME events in the solar corona and in the inner heliosphere, and (2) the evolution of these events through CME‚  CME and CME‚  solar-wind (CME-SW) interactions.

This session will focus on the following core science questions related to extreme events associated with interacting CMEs:

1. What key observational signatures can serve as early indicators of extreme, multi-CME events? (e.g., eruption timing, coronal magnetic complexity, signatures of CME preconditioning, shock formation)

2. How do complex CME‚  CME and CME‚  SW interactions modify the heliospheric evolution of CMEs, including their kinematics, shocks, and magnetic structure?

Session Summary

The goal of this session was to facilitate discussions on complex CME interactions that lead to extreme events.

Major Discussion Highlights:

1. Connections between coronal and heliospheric observations of extreme events at Earth.
2. Are extreme events always associated with multiple interacting CMEs or single large events can be equally extreme? Examples of single events versus multiple CMEs were highlighted.
3. Physical mechanisms of shock-shock, shock-ejecta, and multiple ejecta interactions. Nature of these interactions where seemingly boring CMEs produce extreme signatures.
4. Challenges when modeling multiple CMEs to capture detailed physics. Point raised on careful consideration of different model capabilities and correctly interpreting the results. Specifically for CME-CME interactions, models that do not include magnetic structure of CMEs are not feasible to capture the physical interaction mechanisms.
5. Improved complex CME descriptions are required for suitable reconstruction of the CME properties. Discussion on the role of the ambient solar wind, and models that start on the Sun versus at 0.1 AU.
6. Finally, we discussed the capabilities that are still lacking when using numerical models to capture complex CME interactions that cause extreme signatures. And the possible use of multipoint observations to mitigate these.

After last year’s session (in 2025), this year we focused more on connecting the modeling and observations, identifying limitations in both areas. For future sessions, we may explore going back to fundamental descriptions of what extreme events are, and the associated physical mechanisms that make them extreme.

Talwinder Singh (GSU); Evangelia Samara (NASA/CUA); Ronald Caplan (PSI); Dinesha Hegde (UAH)

Scene Setters: Cooper Downs (PSI); Elena Provornikova (APL)

Data-driven heliospheric MHD modeling remains one of the best methods to characterize and forecast space weather (SW) conditions in the inner heliosphere. Over the past few years, time-dependent solar wind driving has become increasingly prevalent, with the community moving toward it as a more reliable approach. This session will address  the central challenge of integrating observational data into time-dependent solar wind models while preserving physical consistency and predictive skill. We will discuss how well current time-dependent modeling approaches reproduce the variability observed both in situ and remotely, including transient structures. A key subject is identifying where uncertainties arise (from observations, data-assimilation/conditioning choices, model physics, numerical methods, and initialization), and discussing practical strategies to quantify and mitigate these uncertainties for more reliable space-weather applications.

1. What are the most effective strategies for integrating observational data into time-dependent solar wind models?

2. How well can current time-dependent solar wind models capture the variability observed in-situ/remotely?

3. Where do the uncertainties in the modeling results arise?

Session Summary

This session was focused on various ways, the modeling community is trying to capture the realistic time-dependent nature of the corona and inner heliosphere. Recent developments, challenges, and future possibilities were discussed.

1. Different approaches for introducing time dependence into coronal and inner-heliospheric models were discussed, including continuously updating the boundary conditions and interpolating between a sequence of steady-state solutions.
2. Current sources of uncertainty were examined, including uncertainties within the models themselves and in the observational data used to constrain them. Ron Caplan gave a short presentation comparing different inner-heliospheric models driven by the same boundary conditions.
3. The group discussed what a realistic first step toward improving modeling accuracy might be, including whether increasing ensemble spread could help better encompass the observations.
4. Ongoing community efforts to perform continuous, time-dependent solar-wind simulations were reviewed. Graduate student Gergely Koban gave a short presentation on this topic.

A promising future direction for this session will be a slightly more focused session on how the newly available data from PSP and SolO can help constrain the time-dependent models further.

Norberto Romanelli (UMD/NASA GSFC), Cecilia MacCormack (CUA/NASA GSFC), Eleni Nikou (NRC Research Associate, U.S. Naval Research Laboratory), Teresa Nieves-Chinchilla (NASA GSFC)

Scene Setting Speakers: Christina Kay (APL) – Shaosui Xu (Space Sciences Laboratory, UC Berkeley)

The evolution of large-scale solar structures across the solar system, such as coronal mass ejections (CMEs), high-speed solar wind streams, and co-rotating interaction regions (CIRs), has been extensively studied using a variety of observations from space instruments and simulation models. While these efforts have significantly advanced our understanding of these structures, a more comprehensive approach is still needed to better discern the processes that influence their evolution as they propagate through the inner heliosphere. As these structures move outward from the Sun, they undergo complex interactions with the solar wind and magnetic fields, ultimately influencing their effects on planetary environments. Understanding the physical processes that drive the evolution of these solar transients, both within 1 AU and beyond, is critical for improving space weather forecasting at Earth and Mars. This session will address key questions regarding the physical mechanisms governing the evolution of these solar structures and their implications for planetary space weather.

Question 1: What are the main sources of uncertainty in describing and tracking the evolution of CMEs within 1 au- observational constraints, model assumptions, or their coupling?

Question 2: How do Earth-validated prediction methods perform when applied to Mars, and what are their main limitations?

Question 3: How does the Martian environment respond to space weather driven by CMEs, and how does this response vary with CME properties and configuration?

Session Summary

This session examined how large-scale solar-wind structures, especially CMEs, CME-driven shocks, high-speed streams, and interaction regions, evolve through the inner heliosphere and drive space-weather effects at Earth and Mars. The discussion emphasized the connection between Sun-to-Earth and Sun-to-Mars propagation, observational and modeling uncertainties, the transferability of Earth-validated prediction methods to Mars, and the response of the Martian hybrid induced/crustal-field magnetosphere and upper atmosphere.

The session addressed the physical processes governing the evolution of CMEs and their implications for space weather forecasting at both Earth and Mars. We highlight a few key points here:

On operational forecasting:

Discussion centered on identifying which observational gaps (in cadence, spatial coverage, or instrument sensitivity) introduce the greatest uncertainty when tracking CMEs below 1 au. The group also examined the tools currently used operationally, such as the cone model and ENLIL, discussing their known limitations and the resulting errors in arrival time and geoeffectiveness predictions. A related and still-open question is whether uncertainty in the background solar wind state dominates over uncertainty in the CME itself when forecasting transit times, since these two sources of error are difficult to disentangle with current operational tools.

On Mars space weather:

The group discussed how in-situ coverage at Mars still has significant observational gaps due to available instrumentation and orbital geometry, compared to its terrestrial counterpart, particularly regarding continuous upstream monitoring. The session also considered the reconstruction problem: when upstream solar wind or IMF measurements are not available at Mars, how reliably can the incident space weather driver be reconstructed from other available data? This connects to a broader question of what minimum measurement set is needed to establish cause and effect at Mars (e.g., vector IMF, solar wind moments, SEP spectra, EUV/soft X-ray irradiance), and how much a dedicated Mars L1 monitor could improve outcomes for both science and operational forecasting. Finally, the group discussed how impacts at Mars could be measured going forward, including whether new, Mars-specific space weather indices are needed.

Outlook for scientific and practical developments:
Progress on the questions discussed will likely require a combination of improved observational strategies within 1 au to address the cadence and coverage gaps identified for CME tracking, continued in-situ monitoring at Mars, and the development of Mars-specific validation metrics and indices rather than a direct adoption of Earth-based forecasting frameworks.

Future Sessions:
A natural follow-on session would focus on “Benchmarking Space Weather Forecasting Across Planetary Environments,” extending the Earth–Mars comparison discussed here into a more systematic framework for adapting and validating forecasting tools across different heliocentric distances.

Ricky Egeland (NASA JSC), James Ryan (UNH), Nariaki Nitta (LMSAL), Pierre-Simon Mangeard (Deleware), Claudio Corti (University of Hawaii, NASA GSFC CCMC),  Kathryn Whitman (KBR, NASA JSC SRAG)

Scene Setters: Alessandro Bruno (NASA GSFC; Catholic University of America), Junxiang Hu (NASA GSFC; University of Alabama, Huntsville)

There has been recent interest in the capability to understand and predict extreme solar energetic particle events. After a generally quiet solar cycle, two very recent events in Solar Cycle 25, 2025-11-11 (Veteran’s Day Event) and 2026-01-18 (MLK Day Event), were both extreme in very different ways. The Veteran’s Day Event (GLE 77) showed a very hard spectrum with a strong energetic storm particle phase that was observed even at >500 MeV. Neutron monitors up to very high cutoffs observed the event within minutes following the source eruption on the Sun. The MLK day event was associated with a strong Forbush decrease and was the third highest intensity SEP event measured by GOES in the >10 MeV channel since 1986, but had only a very weak enhancement at high energies. This session aims to explore what the measurements from our current heliophysics and space weather fleet and neutron monitors on the ground can tell us about these events. Can we explain what conditions and solar and heliospheric phenomena lead to their extreme natures and how might this apply to extreme events in general? How can we develop predictive models for extreme SEP events? We invite attendees to bring measurements, analyses, interpretations, modelling results and questions for a lively discussion about these challenge events.

Are extreme events drawn from the same distribution of associated properties of active regions, flares, and CMEs, and background solar wind as small events, or is there something peculiar about them? 

What is the role of magnetic connectivity, interplanetary CMEs, previous solar and heliospheric activity, and the presence of strong energetic storm particle (ESP) phases during the passage of an Earth-bound CME?  

What was the nature of the impulsive spike and the evolution of the subsequent anisotropy of the late phase of GLE77, until the arrival of a CME?

Campaign Events: 

2025-11-11 (Veteran’s Day Event)
2026-01-18 (MLK Day Event)

Participants are solicited to bring data and simulations of all related phenomena (active regions, corona, solar wind, flares, CMEs, particles) for the challenge events in order to drive conversation and interpretation of the events. You may prepare a single slide ahead of time to share during the session (as conversation allows). The slides may be uploaded to: https://drive.google.com/drive/folders/1Pg2Qzw0wok2qi-p6MujWlFaYGDf43ps4?usp=sharing . After SHINE, contributions will be posted to the website and used in writing an informal summary report of the challenge outcomes with credit given to all contributors.

View all presentations, including scene setters: https://drive.google.com/drive/folders/1FSUz5CZc54EejnzZjaAQ7msthJASXyii?usp=sharing

Session Summary

This session discussed two recent large Solar Energetic Particle (SEP) events: November 11, 2025 (Veteran’s Day Event) and January 18, 2026 (MLK Day Event). Although both events were extreme, they followed fundamentally different pathways to producing severe space weather. The November 2025 event produced GLE #77—the fourth strongest ground level enhancement in the neutron monitor era in terms of integral intensity—and was characterized by an unusually hard energy spectrum, preceding CMEs, and a highly disturbed heliosphere. In contrast, the January 2026 event produced exceptionally high low-energy proton intensities (~37,000 pfu in GOES >10 MeV), a prolonged shock-associated energetic particle enhancement, and an intense Forbush decrease while propagating through relatively undisturbed interplanetary conditions. The session explored how differences in the solar eruption, CME/shock evolution, magnetic connectivity, heliospheric preconditioning, particle transport, and local shock processes combined to produce these contrasting forms of extremeness. The discussion was broken into two parts, with Alessandro Bruno leading the discussion of the observational features of these extreme events and Junxiang Hu discussing the modeling challenges, in particular modeling Energetic Storm Particle enhancements.

Both the scene-setting speakers and the session participants brought forward a large variety of observational data and analyses of the two extreme events. The complex sequence of events leading up to the November 2025 event were outlined and discussed, with the hard-spectrum GLE associated with the third SEP enhancement from the source active region, followed later by a sequence of shocks from earlier eruptions that produced an unusual shock-associated energetic particle enhancement.. A large variety of associated phenomena were presented and discussed, including active region evolution, associated X-ray and gamma ray signatures, radio observations (EOVSA), EUV waves, CME kinematics & shock front observations, shock properties, magnetic connectivity, and interplanetary preconditioning. Detailed event characteristics from space-based particle detectors, including those off the Earth-Sun line such as Solar Orbiter and Biosentinel, and the ground-based neutron monitor network, as well as the gLOWCOST Muon Detector Network were evaluated. Early modeling results from iPath, CORHEL CME flux ropes, and dose estimates from HZETRN2020 were presented and discussed.

Significant questions remain related to distinguishing these extreme events from other similar conditions. Why was the November 2025 event spectrum so hard, and how was the interplanetary preconditioning distinct from other similarly active time periods that did not result in extreme hard events? Why did the Jan 2026 event produce such exceptionally high low-energy proton intensities and a strong shock-associated particle enhancement, yet only a weak relativistic component? How did magnetic connectivity affect the event characteristics, and how did the energetic particle populations evolve in interplanetary space? What roles did heliospheric preconditioning, particle transport, and local shock evolution play in shaping the observed event characteristics? How can we properly model events with multiple CMEs? The session participants gathered together a large number of observations to bear on the problem of understanding these extreme events. Addressing these outstanding questions will require continued observational and modeling efforts. What additional observation capabilities are needed to address the modeling challenges? These two events are relatively recent and many participants are working on publishing analyses. There was some interest in the prospect of a large collaborative effort to analyze and publish the data and model results gathered for this session.

Manuel Cuesta (Princeton University), Richa Jain (Princeton University), Gabriel Muro (California Institute of Technology), Zigong Xu (California Institute of Technology)

Scene Setting Speakers: Bishwas Shrestha (Princeton University) and Savvas Raptis (Johns Hopkins University Applied Physics Laboratory)

In this SHINE session, we ask how are different particle populations injected into acceleration regions throughout the inner heliosphere, what distinguishes their source conditions, and how do properties of a coronal mass ejection (CME) affect the geo-effectiveness of a solar event? IMAP‚  unique capabilities at 1 au captures a mixture of solar wind ions and electrons, suprathermal particles, and interstellar pickup ions, yet the pathways by which these populations transition from thermal to suprathermal energies remain poorly constrained. Understanding whether injection is dominated by turbulence, reconnection, shocks, or boundary-layer processes is crucial. Framing the problem in this way invites discussion of how IMAP can provide closure on competing mechanisms by leveraging composition, pitch-angle structure, and spectral signatures. Our goal is to understand how these effects can unfold through the many perspectives that IMAP offers, as well as examine the spatiotemporal structures when combined with other spacecraft at or within 1 au. We also invite discussion surrounding simulations to help explain unique properties of particle acceleration and transport observed in situ.

1.  Can we quantify the energization of pickup ions and determine its contribution to the acceleration of suprathermal particle populations?

2.  How can the L1 spacecraft fleet improve our determination of the mesoscale structure of the solar wind and large-scale transients?

Session Summary

The main theme of the session was the exploration of particle populations, how they are different under regular solar wind conditions and near shocks, as well as asking the question of how multi-spacecraft efforts can aid our understanding of what mechanisms drive those differences.

We discussed two main science questions: (1) How can we apply what we have learned about pickup ion acceleration in the outer heliosphere and apply it to anticipated observations near 1 au and (2) how we can leverage the constellation of spacecraft near 1 au to achieve a deeper understanding of solar wind structures that drive the acceleration of charged particles, including pickup ions?

One main question brought up during the first half of the session involved whether formalism surrounding the spatial diffusion of pickup ions has been explored, and how it would differ to the spatial diffusion of solar energetic particles derived from solutions to the Parker or focused transport equations. We had participation from both early-mid career and late career folks, as well as some input on recent simulation work. During the second half, we had active discussion involving reconstruction of an interplanetary shock observed by the L1 spacecraft constellation, which stemmed from whether or not differences in shock geometry estimates characterize physical structure or error in method.

Future research directions include (1) improvements of out-of-ecliptic reconstructions of shocks to assist in the connection between shock orientation and geoeffectiveness, (2) use separations of spacecraft across longitudes to assist in understanding the time variability of the pickup ion distribution near 1 au, and (3) understanding the mechanisms for spatial and velocity diffusion of pickup ions near shocks. Sessions in the future should target each of these research directions separately, which may help inform coordination of future flight missions to optimize the requirements necessary to move forward on these topics.

Parisa Mostafavi (Johns Hopkins University APL), Christina Cohen (California Institute of Technology), Savvas Raptis (Johns Hopkins University APL)

Scene Setting Speakers: Immanuel Jebaraj (Department of Physics and Astronomy, University of Turku, Finland), Bishwas Shrestha (Princeton University)

Shock waves are a fundamental plasma process throughout the heliosphere, driving energy dissipation, particle acceleration, and large-scale heliospheric structure. In the inner heliosphere, shocks associated with solar eruptions, stream interaction regions, and planetary bow shocks strongly influence solar energetic particle (SEP) production and transport. As shocks propagate outward, their structure and dynamics evolve and change dramatically as solar wind conditions change and the influence of energetic pickup ions (PUIs) and anomalous cosmic rays (ACRs) increases in the outer heliosphere. Recent observations from Parker Solar Probe, Solar Orbiter, near-Earth missions, New Horizons, and Voyager, together with advances in theory and modeling, now enable shocks and energetic particles to be studied across an unprecedented range of heliocentric distances. This session aims to bring together the full heliospheric community working on shocks and energetic particles associated with them into a single, discussion-focused forum.

1.    What physical processes govern the formation, structure, and evolution of shocks throughout the diverse environments of the heliosphere?

2.  How do shocks regulate energy conversion, particle acceleration, and plasma heating across the heliosphere under different plasma conditions? and how do these mechanisms couple with background interplanetary turbulence and transport processes?

3.  What are the key observational and theoretical challenges in understanding heliospheric shocks and energetic particles, and how can they be addressed?

Session Summary

This session focused on the fundamental physics of collisionless shocks and energetic particles across the heliosphere, from the near-Sun environment to the outer heliosphere. Rather than organizing discussions around individual missions, the session emphasized the physical processes governing shock formation, evolution, plasma heating, and particle acceleration across diverse plasma environments. By bringing together researchers working on observations, theory, and modeling, the session provided a forum to compare shock physics across heliocentric distances and to identify the common processes and key differences that emerge under changing plasma conditions.

The session was highly interactive, with discussions beginning during the scene-setting talks and continuing throughout both blocks. To encourage participation from scientists with diverse backgrounds, the organizers intentionally asked fundamental questions during the talks, creating opportunities for speakers to explain key concepts and ensuring that students and early-career researchers could actively engage in the discussion. This approach resulted in a lively exchange between senior scientists, early-career researchers, and students.
The first block focused on the multi-scale nature of collisionless shocks, including particle injection, wave-particle interactions, diffusive shock acceleration, and the challenge of connecting MHD and kinetic physics. The second block extended these discussions to the outer heliosphere, highlighting the role of pickup ions in modifying shock structure, plasma heating, and particle acceleration. Short contributions by Carlos Braga, Parisa Mostafavi, and Pontus Brandt helped bridge the gap between inner and outer heliosphere studies by connecting CME-driven shocks, pickup ions, and energetic particles across heliospheric distances. Participants commented that they learned substantially from the discussions, particularly from the comparisons between different heliospheric environments.

The session demonstrated the value of bringing together researchers from the inner and outer heliosphere, energetic particle, and modeling communities to address common scientific questions. Discussions continued well beyond the scheduled session, leading to new collaborations and strengthening existing ones. Several promising research directions emerged, including tracking CME-driven shocks from the Sun to the outer heliosphere, understanding how pickup ions modify shock structure and cosmic-ray transport, investigating the role of energetic particles in modifying shocks from near-Earth space to the termination shock, and improving the coupling between kinetic and fluid-scale models. The enthusiastic participation and positive feedback highlighted the need for continued discussion-focused, cross-disciplinary sessions that connect heliospheric communities through the shared physics of shocks and energetic particles.

Prateek Mayank (SWx TREC University of Colorado); Nishtha Sachdeva (University of Michigan); Aatiya Ali (Georgia State University)

Scene Setters: Andrés Muñoz-Jaramillo (SwRI, Boulder) and Vishal Upendran (SETI)

Machine Learning (ML) is increasingly used in space weather research, with growing success across forecasting, classification, and surrogate modeling. Despite this rapid adoption, the community lacks widely accepted guidelines for model design, evaluation, reproducibility, and interpretation. This gap motivates the need for focused community-driven discussions. This session aims to move beyond isolated ML applications and address a central question: How do we evolve from individual ML successes toward a unified, trustworthy, and reproducible framework for space weather prediction?

1. What ML applications have demonstrated robust and reproducible performance in space weather forecasting?  

2. How should metrics and model architectures be chosen to match specific space weather problems?  

3. What practices should be adopted for benchmarking, validation, and interpretation of ML models?

Session Summary

The goal of this session was to facilitate discussions on current ML approaches for forecasting space weather drivers and how they can be transformed into a trustworthy community-driven framework.
It was structured around major training challenges, architecture, benchmarking and community incentives.

1. Current machine learning forecasting methods continue to be constrained by dataset distribution issues and class imbalances, necessitating focused strategies to mitigate these shortcomings.
2. Enhancing and standardizing evaluation metrics for comparable models is critical for advancing the field, as conventional metrics often fail to adequately assess performance.
3. Significant progress has been made in developing ML architectures tailored for physical systems. While novel architectures should be explored, increased complexity does not inherently guarantee superior performance than simpler ones.
4. To accurately evaluate the real-world benefits of machine learning approaches, community-led benchmarking initiatives must be established across all space weather drivers.
5. The NASA SDMC30 AI roadmap offers a structured framework for implementing community incentives, which is uncovered in the current NASA Decadal Survey.

This session focused more on broader and common aspects of ML modeling for space weather drivers. However, due to limited time, we couldn’t have in-depth discussion about specific drivers of space weather.

For the next SHINE, we would like to explore more specific discussion on one/two space weather drivers (e.g., solar wind, etc), such that both prediction and research aspects can be covered.

Weihao Liu (University of Michigan), Claudio Corti (University of Hawaii, NASA GSFC CCMC), Kathryn Whitman (KBR, NASA JSC SRAG), Ashraf Moradi (University of Arizona)

Scene Setting: Arik Posner (NASA JSC SRAG); Antonio E. Niemela (University of Maryland; NASA Goddard Space Flight Center)

Parker Solar Probe and Solar Orbiter are taking measurements in new heliospheric regimes, while numerous spacecraft throughout the heliosphere, e.g., the STEREO satellites and spacecraft at Mars, have now accrued measurements for many years. This makes now an opportune time to revisit the long-standing problems of solar energetic particle (SEP) acceleration and transport, considering the full energy spectrum from keV to GeV. The first part of the session will focus on acceleration mechanisms and inconsistencies in current explanations. The second part of the session will turn to particle transport, including cross-field diffusion and drift effects, and the impact of heliospheric structures on transport outcomes.

What do new multi-point observations and analyses tell us about SEP acceleration and   transport processes? 

How do these processes apply to particles across the full energy spectrum, including hundreds of MeV to GeV?  

How do other heliospheric phenomena, like solar wind structure, interplanetary CMEs, or previous eruptive activity impact these SEP processes?

Session Summary

Based on Parker Solar Probe, Solar Orbiter, and multipoint observations across the heliosphere, this discussion-driven session reassessed SEP acceleration and transport as observed across keV-to-GeV energies. Part I examines flare-site acceleration, CME-driven shocks, and the limitations of the impulsive/gradual paradigm. Part II examines parallel transport, field-line random walk, cross-field diffusion and drift, turbulence, and the influence of heliospheric structure. The aim of this session is to identify where prevailing explanations fail and what evidence is needed for an event-wide, predictive account of SEPs.

The session does not fully resolve the flare vs. shock debate, but it narrowed the problem that the source acceleration, seed populations, magnetic connectivity, and transport cannot be inferred independently. We reach a relatively broad agreement that both flare- and shock-related acceleration contribute to SEP events, while their relative importance varies from event to event. Our discussion broadly favors event-specific, composite interpretations over a universal two-class picture, while it preserves important disagreements about the SEP event timing and energy dependence.

The future progress requires coordinated multipoint observations, improved measurements of suprathermal seed populations, and models that starts from the low corona to the heliosphere while incorporating realistic shock evolution and particle transport. The model–observation validation should use shared benchmark events and compare onsets, spectra, and anisotropy, rather than focusing only on timing or peak flux. A follow-on SHINE effort is to combine observations and modeling to investigate the roles of seed particles and parallel and perpendicular transport, including their contributions to dropout events and the production of particles above 500 MeV as observed in extreme events.

Nour E. Raouafi – Johns Hopkins Applied Physics Laboratory, Laurel, MD 20723; Arik Posner – SMD Heliophysics Division, NASA Headquarters

Understanding how the solar corona is heated to millions of degrees and how the solar wind and energetic particles are accelerated near the Sun remains one of the most fundamental challenges in heliophysics. Over the past decade, transformative observations from Parker Solar Probe, Solar Orbiter, DKIST, SDO, and complementary ground- and space-based observatories have provided unprecedented access to the key physical regimes where these processes operate. These measurements have revealed complex, multi-scale dynamics‚  including waves, turbulence, reconnection, fine-scale structuring, and direct links between coronal structures and the nascent solar wind‚  that were previously inaccessible. Together with advances in theory and numerical modeling, these results have significantly narrowed the range of viable mechanisms. The central question now is whether this progress is sufficient to move from competing explanations toward closure‚  and what observational, theoretical, and modeling gaps must still be addressed to fully understand coronal heating and near-Sun acceleration processes.

Given recent advances from Parker Solar Probe, Solar Orbiter, DKIST, and related observatories, what key physical processes are now established as drivers of coronal heating, and what critical evidence is still missing to reach closure?
 
How have near-Sun observations reshaped our understanding of solar wind acceleration, and what remaining observational or theoretical gaps must be closed to fully explain the origin and properties of the solar wind?
 
What progress has been made in identifying the mechanisms responsible for particle energization and transport near the Sun, and what is required to achieve a predictive understanding of these processes across the heliosphere?

Michael Terres (CfA), Kris Klein (University of Arizona), Tamar Ervin (Univ. California Berkeley), Srijan Bharati Das (Center for Astrophysics)

Scene Setting Speakers: Steven Cranmer (University of Colorado Boulder), Evan Yerger (University of New Hampshire)

Dissipation and damping are fundamental processes by which free energy is transferred from electromagnetic fluctuations to particle species. Despite decades of study, the specific mechanisms driving this energy exchange at ion and electron kinetic scales remain fiercely debated. This session addresses a growing dichotomy in our understanding of the near-Sun solar wind. On the one hand, observations in the low-beta inner heliosphere reveal a prevalence of Ion Cyclotron Waves (ICWs), supported by recent theoretical frameworks such as the “helicity barrier,” which suggest that resonant processes are the primary driver of heating. On the other hand, analyses of fluctuations in the sub-Alfvénic region indicate that stochastic heating rates are consistent with the observed turbulent cascade. This presents a fundamental conflict: does the turbulent cascade stall and generate resonant modes, or does it proceed to drive non-resonant stochastic heating?

In this SHINE Session, we seek to address the following three science questions:

1.) How do evolving heliospheric conditions modulate the dominant pathway for energy conversion: is it driven by the damping of the turbulent cascade (via resonance or stochasticity), or by the relaxation of locally generated kinetic instabilities (driven by beams and drifts)?

2.) Can modern analysis techniques definitively distinguish between signatures of resonant and non-resonant heating mechanisms?

3.) Do the ion cyclotron waves observed in the inner heliosphere result from a “helicity barrier” blocking the turbulent cascade, or are they generated locally by kinetic microinstabilities with distinct sources of free energy?

Session Summary

This session explored the fundamental processes that govern damping and dissipation in the corona and inner heliosphere. The discussion largely focused on how free energy is transferred from electromagnetic fluctuations to particle species. We had two scene-setting speakers, Dr. Steven Cranmer and Dr. Evan Yerger, who presented primarily on the observational signatures of solar wind heating and the theoretical processes that are driving turbulent dissipation, respectively. The primary science questions sought to address the dominant heating mechanisms, how the heliospheric conditions govern them, and how the numerously observed ion-cyclotron waves are generated. Dr. Cranmer focused on the first two questions, and Dr. Yerger focused on questions one and three, with discussion of observations and models in both portions. Additionally, the sessions discussed the possible observations and techniques needed to bring closure to the heating processes in the solar wind. This session focused heavily on early-career involvement, with three of the session organizers and one of the scene-setting speakers being early-career professionals, and nine contributed slides from students and post-docs throughout the session, as relevant to the discussion.

The session featured robust discussions on the mechanics of energy conversion, contrasting theoretical models with observational data. The primary mechanisms discussed in this session included stochastic heating and differential streaming, the helicity barrier and imbalanced turbulence, and quasi-linear diffusion and wave generation. Furthermore, the role of imbalanced versus balanced turbulence was discussed.

As highlighted by Niranjana Shankarapa in a student contribution, left-hand ion cyclotron waves are observed almost ubiquitously near the Sun, except in the vicinity of the heliospheric current sheet. This prevalence suggests that resonant processes are a key driver of heating in the low-beta inner heliosphere. As noted during the session, the actual processes driving these waves depend critically on the overall balance of the turbulence. In balanced turbulence, power is retained in broadband fluctuations, leading to stochastic heating. Conversely, in imbalanced intervals, power is concentrated at resonant frequencies; oblique waves destabilize the proton distribution functions, pushing them toward higher perpendicular temperatures and resulting in the emission of parallel ion cyclotron waves. Anchoring these theoretical frameworks in observations, Tamar Ervin highlighted that analyses of fluctuations in sub-Alfvénic intervals indicate that turbulent and stochastic heating rates are consistent. However, these observations fall within an interval of imbalanced turbulence, raising questions about the robustness of current theoretical frameworks.

A significant portion of the subsequent discussion focused on minor-ion heating and its observational signatures. Aidan Nakhleh presented differential streaming observations from ACE, comparing them with theoretical predictions for stochastic heating rates as a function of streaming speed to probe the underlying turbulent cascade. This was contrasted with observations shown by Dr. Cranmer, comparing heavy-ion measurements with predictions of resonant heating. Building on the wave-generation theories discussed earlier, Michael Zhang presented simulations of heavy ions in imbalanced turbulence, demonstrating that the inversion of the m/q temperature-ratio dependence can be explained by parallel waves generated by the helicity barrier. The group also debated whether anisotropic distributions of minor ions independently excite instabilities; it was noted that while helium (alphas) significantly impacts dispersion and the helicity barrier, heavier minor ions likely have less influence. These varying responses of different ion species to the turbulent cascade highlight the necessity of tracing composition-dependent transport.

Looking ahead, the community faces several critical challenges in fully resolving the pathways of solar wind and outer coronal dissipation and damping. A key area for future investigation is understanding the interplay between different dissipation mechanisms, such as magnetic reconnection, turbulent dissipation, and fluid instabilities, which, while subtle, are fundamental to determining how the heliospheric plasma ultimately evolves. Additionally, the role of intermittency must be better integrated into current heating models; as discussed during the session, the generation of parallel waves is highly intermittent rather than volume-filling. Minor ion heating will also remain a crucial in-situ observational frontier. Because alpha particles significantly impact wave dispersion, accurately tracing composition-dependent transport and understanding exactly how heavier ions absorb energy from the turbulent cascade will be essential for constraining kinetic models. Complementing these in-situ efforts, advancements in remote sensing, building on Dr. Steven Cranmer’s discussions of basal coronal heating, will be vital. Since the immediate near-Sun environment remains beyond direct probing, advancing remote sensing capabilities is essential to understanding how closed-field coronal heating processes set the initial conditions for the open-field solar wind. Finally, advancing these theories will require untangling how these different processes interact, a challenge perfectly encapsulated by Dr. Evan Yerger’s concluding question to the group: Can there be an imbalanced stochastic heating that pushes velocity distribution functions along quasi-linear contours? Answering these questions in future studies will ultimately require the targeted integration of high-resolution particle measurements, remote sensing data, simulation-informed reconstructions, and robust cross-disciplinary collaboration. A full understanding of these processes will inform decisions made by modelers on how they drive heating in simulations. This could be a natural extension of this discussion for a future interdisciplinary SHINE session.

Lingling Zhao (University of Alabama in Huntsville); Trevor Bowen (University of California, Berkeley); Yan Yang (University of Delaware)

Scene Setting Speakers: Chen Shi (Auburn University); Senbei Du (Boston University)

Throughout the heliosphere, turbulence mediates the transfer of energy from large-scale MHD motions to kinetic scales. Observations from Parker Solar Probe and Solar Orbiter show that this cascade is highly intermittent, organized by coherent structures, current sheets, and transient phenomena such as magnetic switchbacks. Intermittent structures are also identified beyond 1 au and in the interstellar medium by Voyagers. These features can regulate kinetic-scale wave activity and the energization of suprathermal particle populations. This session will explore the origin, evolution, and dissipation of solar wind turbulence, and how multi-scale structures and kinetic processes shape particle distributions and energization. By integrating observations with theoretical and numerical modeling, the session aims to advance a comprehensive understanding of how turbulence shapes the heliospheric plasma.

1, How does turbulence evolve across various heliospheric boundaries, including the Alfvén critical surface, heliospheric termination shock, and heliopause?

2, How and where does the cascade transition from MHD to kinetic scales in the solar wind and local interstellar medium?

3, How does turbulent reconnection regulate kinetic waves and suprathermal particle energization in the heliosphere?

Session Summary

Session #19 focused on the evolution of solar wind turbulence across multiple scales, spanning MHD to kinetic physics. A central theme throughout the session was the longstanding question of how energy is transported from the solar surface into the solar wind and ultimately dissipated. Presentations highlighted the use of polytropic indices to quantify solar wind heating and identified magnetic reconnection and wave-driven turbulence as two of the primary mechanisms responsible for coronal heating and solar wind acceleration. The session also reviewed the foundations of turbulence theory, beginning with the classical Kolmogorov cascade and its extension to incompressible MHD turbulence. At kinetic scales, turbulent energy is thought to dissipate through several processes, including wave-particle resonances, stochastic ion heating, and intermittent structures associated with magnetic reconnection.

The discussion then expanded to the outer heliosphere, where turbulence is strongly influenced by pickup ions (PUIs). Kinetic instabilities, such as ion cyclotron and mirror instabilities, generated by PUIs provide an important source of turbulence in the outer heliosphere. The heliospheric termination shock (HTS) further modifies the turbulent environment by amplifying pre-existing fluctuations while simultaneously generating unstable particle distributions that can drive additional wave activity.

The session concluded by highlighting several outstanding questions that define the current research frontier. These include understanding how the highly Alfvénic turbulence observed near the Sun evolves and dissipates as the solar wind expands; developing more accurate estimates of the turbulent energy cascade rate using multi-spacecraft observations; and incorporating non-local energy transfer into existing turbulence models. Additional open questions concern the relative contributions of magnetic reconnection and wave/turbulence to plasma heating, the physical mechanisms responsible for energy dissipation at kinetic scales, and the roles of viscosity and resistivity in collisionless plasmas.

Other important topics included the influence of compressibility and magnetosonic waves on critical balance, the extent to which the solar wind can be approximated as incompressible, and the physics governing magnetic switchbacks, including their dependence on plasma beta and their evolution with heliocentric distance. Finally, the applicability of the widely used 2D+slab turbulence model in the high-beta outer heliosphere remains uncertain, as do the origins of the high magnetic compressibility observed in the heliosheath and the some of the local interstellar medium region. A related unresolved question is whether turbulence and kinetic instabilities are sufficient to fully isotropize pickup ions or whether these particles retain significant anisotropies throughout their evolution.

Future research will continue to focus on understanding how highly Alfvénic turbulence evolves and dissipates as the solar wind expands from the corona into the outer heliosphere. A major priority is identifying the physical mechanisms responsible for energy dissipation at sub-ion scales, including the roles of wave-particle interactions involving ion cyclotron waves and kinetic Alfvén waves, as well as determining whether dissipation is governed by reconnection-related processes, effective viscosity, or resistivity in collisionless plasmas. Improving turbulence theories by incorporating non-local energy transfer and compressible fluctuations remains an important challenge for developing more realistic models of solar wind turbulence.

The interaction between turbulence and large-scale heliospheric structures will also be an active area of investigation. Future studies will examine how the termination shock modifies pre-existing solar wind turbulence through wave amplification, mode conversion, and particle acceleration. Outstanding questions include whether foreshock waves exist upstream of the termination shock and whether commonly used turbulence models, such as the 2D+slab model, remain applicable in the high-beta plasma environments of the heliosheath and local interstellar medium.

Continued analysis of data from recent and upcoming multi-spacecraft missions will enable more accurate measurements of turbulence evolution, energy cascade rates, and kinetic dissipation processes over a broad range of heliocentric distances. Coordinated observations from multiple spacecraft, together with advances in numerical simulations and theoretical modeling, will be essential for addressing these outstanding questions.