3He-rich SEP Events Observed by STEREO-A

TL;DR

This study analyzes 3He-rich solar energetic particle events observed by STEREO-A during solar cycle 24, revealing their association with active regions near coronal holes and their distinct compositional signatures.

Contribution

It provides detailed observations of 3He-rich SEP events, highlighting their characteristics, timing, and association with solar wind features and active regions, expanding understanding of their origins.

Findings

Six 3He-rich SEP events identified with high 3He/4He ratios.

Most events linked to high-speed solar wind streams and active regions.

Events showed enhanced NeS/O and Fe/O ratios.

Abstract

Using the SIT (Suprathermal Ion Telescope) instrument on STEREO-A we have examined the abundance of the rare isotope 3He during the rising activity phase of solar cycle 24 between January 2010 and December 2011. We have identified six solar energetic particle (SEP) events with enormous abundance enhancements of 3He (3He/4He >1). The events were short lasting, typically ~0.5-1 day and most of them occurred in association with high-speed solar wind streams and corotating interaction regions. With one exception the events were not associated with ~100 keV solar electron intensity increases. The events showed also enhanced NeS/O and Fe/O ratios. The solar images indicate that the events were generally associated with the active regions located near a coronal hole.