Recurring 3He-rich Solar Energetic Particle Events

TL;DR

This study analyzes recurring 3He-rich solar energetic particle events during solar cycle 24, revealing variable isotope ratios and consistent solar sources across spacecraft separated by several days.

Contribution

It provides new insights into the timing, source regions, and variability of 3He-rich solar energetic particles using multi-spacecraft observations.

Findings

3He/4He ratio varies significantly in events.

Events observed successively on ACE and STEREO-A show correlated source regions.

Delay times between observations are consistent with solar rotation periods.

Abstract

Using the SIT instrument aboard STEREO we have examined the abundance of the 3He during the ascending phase of solar cycle 24 from January 2010 through December 2012. We report on several cases when 3He-rich solar energetic particle events were successively observed on ACE and STEREO-A with delays consistent with the Carrington rotation rate. In the investigated period ACE and STEREO-A were significantly separated in the heliolongitude corresponding to solar rotation times of 5 to 10 days. We inspect STEREO-A EUV images and use the potential-field source-surface extrapolations together with in-situ magnetic field data to identify responsible solar sources. We find the 3He/4He ratio highly variable in these events and correlated between the spacecraft for the cases with the same connection region on the Sun.