Authors: Vahe Petrosian (Stanford University)

Vahe’ Petrosian, Stanford University, Stanford CA, 94305

Electrons and ions are accelerated in the solar flare re-connection sites and in the associated CME shock environments. Based on the radiative signatures of flares, stochastic acceleration by turbulence appears as a likely acceleration mechanism. Turbulence and magnetic field geometry also govern the transport of particles from the acceleration site flaring loop tops down to the photosphere and out into the solar wind. This has been the primary focus of Solar Physics community. On the other hand, Investigation of gradual SEPs, which are believed to be accelerated by the CME-shocks, has been primarily focus of the heliophysics community. While the seed particles for the flare site acceleration are known to be the background plasma particles, there has been a long standing question about the seed (suprathermal) particles for production of CME-shock accelerated SEPs.

In the past there has not been extensive investigation of the interrelation between the two sites and processes. However, in recent years there has been growing activity in this area due to new theoretical developments and, more importantly, new observations. One important interconnection is the idea that flare accelerated particles, escaping the re-connection site along open field lines connected to the CMEs, could be the seeds for a second phase acceleration by the CME-shock. This view is supported by the dichotomy between impulsive SEPs, with large enhancement of 3He and heavier ions, and gradual ones with nearly photospheric abundances. The second is provided by observation of gamma-rays by Fermi, up to nearly 10 GeV, associated with solar flares, which are often associated with fast CMEs that last many hours, and in same cases originate from flares located behind the limb (BTL) of the Sun. While CMEs are associated with type II radio emission, produced by upstream electrons, the gamma-rays, produced by accelerated protons and ions, can be produced only at the photosphere. This has led to the possible scenario whereby CME accelerated particles escaping the downstream of of the CME-shock toward the Sun could be the source of the gamma-rays, especially for the BTL flares, showing the reverse side of the interconnection.

I will review the observations and briefly describe the models for both acceleration and transport. This is directly connected to the LWS Focus Program on “Origin and Consequences of Suprathermal Particles that Seed Solar Energetic Particles.”