Impulsive Solar Energetic Particle Events: Extreme-Ultraviolet Waves and Jets

Radoslav Bučík

doi:10.3389/fspas.2021.807961

Abstract

Impulsive solar energetic particle (ISEP) events show peculiar elemental composition, with enhanced 3He and heavy-ion abundances, markedly different from our Solar System composition. Furthermore, the events are characterized by a wide variety of energy spectral shapes from power laws to rounded spectra toward the low energies. Solar sources of the events have been firmly associated with coronal jets. Surprisingly, new observations have shown that events are often accompanied by so-called extreme-ultraviolet (EUV) coronal waves–a large-scale phenomenon compared to jets. This paper outlines the current understanding of the linkage of EUV waves with jets and energetic ions in ISEP events.

Highlights

Extreme-ultraviolet (EUV) waves appear as large-scale expanding disturbances in the corona
The EUV waves are regularly observed in coronal mass ejections (CMEs)-driven shock gradual solar energetic particle (GSEP) events (e.g., Torsti et al, 1999; Park et al, 2013; Lario et al, 2014), usually accompanied by large GOES X-ray (1–8 Å) flares (M, X-class)
We review the possible effects of the EUV waves on energetic ions in impulsive solar energetic particle (ISEP) events and their relation to jets

Summary

INTRODUCTION

Extreme-ultraviolet (EUV) waves appear as large-scale expanding disturbances in the corona. With help of improved imaging resolution from Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory (SDO) that provide a full-disk view of the Sun from different observing angles, there have been reported EUV waves in many impulsive solar energetic particle (ISEP) events (Wiedenbeck et al, 2013; Bučík et al, 2015, 2016a; Nitta et al, 2015; Cohen et al, 2021) Though these waves had a smaller spatial scale and were fainter than those in GSEP events, their observations in ISEP events, previously associated with compact flare signatures, were surprising. We review the possible effects of the EUV waves on energetic ions in ISEP events and their relation to jets

ISEP EVENTS

Rate of Occurrence

Delays

Energy Spectra

Longitude Spread

CONCLUSION