Observations of EUV Waves in 3He-Rich Solar Energetic Particle Events

TL;DR

This study reports the observation of EUV waves associated with 3He-rich solar energetic particle events, indicating large-scale disturbances may play a role in their acceleration alongside jets.

Contribution

It provides the first evidence linking EUV coronal waves to 3He-rich SEP events, suggesting a new aspect of their acceleration mechanism.

Findings

EUV waves observed with 3He-rich SEP events without CMEs.

Different spectral classes imply multiple acceleration mechanisms.

EUV waves may contribute to SEP production alongside jets.

Abstract

Small 3He-rich solar energetic particle (SEP) events with their anomalous abundances, markedly different from solar system, provide evidence for a unique acceleration mechanism that operates routinely near solar active regions. Although the events are sometimes accompanied by coronal mass ejections (CMEs) it is believed that mass and isotopic fractionation is produced directly in the flare sites on the Sun. We report on a large-scale extreme ultraviolet (EUV) coronal wave observed in association with 3He-rich SEP events. In the two examples discussed, the observed waves were triggered by minor flares and appeared concurrently with EUV jets and type III radio bursts but without CMEs. The energy spectra from one event are consistent with so-called class-1 (characterized by power laws) while the other with class-2 (characterized by rounded 3He and Fe spectra) 3He-rich SEP events, suggesting different acceleration mechanisms in the two. The observation of EUV waves suggests that large-scale disturbances, in addition to more commonly associated jets, may be responsible for the production of 3He-rich SEP events.