Solar Energetic Particles: Spatial Extent and Implications of the H and He Abundances

Abstract One of the earliest indicators importance shock acceleration solar energetic particles (SEPs) was broad spatial extent “gradual” SEP events produced as waves, driven by wide, fast coronal mass ejections (CMEs), expand across Sun with cross-field transport mediated shocks. Contrasting “impulsive” events, characteristic enhancements 3 He and heavy elements, are now associated magnetic reconnection on open field lines in jets. However, large waves can also traverse pools residual impulsive suprathermal ions jets produce CMEs that drive waves; both cases shocks reaccelerate abundance signatures well plasma. These more-complex “excess protons” identify this process, recently, differences distribution 4 abundances have been found to depend upon combination seed population mode. Extreme may reflect underlying regions being sampled and, surprisingly, where sample two seed-particle populations seem about twice He/O ratio those a single source.