Investigation of energetic particle release using multi-point imaging and in situ observations

TL;DR

This study combines multi-point imaging and in situ data to analyze the timing and mechanisms of energetic particle release during a solar eruption, highlighting the role of shock connectivity and acceleration efficiency.

Contribution

It introduces a method to compare particle release times with shock and EUV wave propagation, providing insights into particle acceleration and release processes during solar eruptions.

Findings

Particle release at L1 coincides with shock contact with magnetic field lines.

STEREO A particle release is delayed due to shock connection timing.

Shock acceleration efficiency influences particle release at different spacecraft.

Abstract

The solar eruption on 2012 January 27 resulted in a wide-spread solar energetic particle (SEP) event observed by STEREO A and the near-Earth spacecraft (separated by 108\degree). The event was accompanied by an X-class flare, extreme-ultraviolet (EUV) wave and fast coronal mass ejection (CME). We investigate the particle release by comparing the release times of particles at the spacecraft and the times when magnetic connectivity between the source and the spacecraft was established. The EUV wave propagating to the magnetic footpoint of the spacecraft in the lower corona and the shock expanding to the open field line connecting the spacecraft in the upper corona are thought to be responsible for the particle release. We track the evolution of the EUV wave and model the propagation of the shock using EUV and white-light observations. No obvious evidence indicates that the EUV wave reached the magnetic footpoint of either STEREO A or L1-observers. Our shock modeling shows that the release time of the particles observed at L1 was consistent with the time when the shock first established contact with the magnetic field line connecting L1-observers. The release of the particles observed by STEREO A was delayed relative to the time when the shock was initially connected to STEREO A via the magnetic field line. We suggest that the particle acceleration efficiency of the portion of the shock connected to the spacecraft determines the release of energetic particles at the spacecraft.