Origin of 3He abundance enhancements in gradual solar energetic particle events

TL;DR

This study investigates the origins of 3He abundance enhancements in high-energy solar proton events, identifying reaccelerated flare material and coronal jets as key factors in 3He enrichment.

Contribution

It provides a detailed analysis of 3He enhancement sources in solar energetic particle events, highlighting the role of reaccelerated flare material and coronal jets.

Findings

Reaccelerated remnant flare material causes 3He enhancements in most events.

Coronal jets are associated with the highest 3He/4He ratios.

Some events' 3He enhancements are due to leftover or independent 3He from previous events.

Abstract

We examined the origin of 3He abundance enhancement in 23 high-energy (25-50 MeV) solar proton events that coincide with 3He-rich periods detected by ACE ULEIS in 1997-2021. In seven events, 3He enhancement was due to 3He leftover from preceding events or independent 3He events occurring during proton events. One event is the most likely impulsive (3He-rich), and another is unclear. Reaccelerated remnant flare material was the most probable cause of 3He enhancements in the remaining 14 proton events. Imaging observations showed coronal jets in the parent active regions in six of these 14 events. Remarkably, the highest 3He/4He occurred in events with jets, implying their contribution to 3He enhancement.