Fermi Detection of \gamma-ray emission from the M2 Soft X-ray Flare on 2010 June 12

TL;DR

This paper reports on Fermi observations of a modest M2 solar flare that nonetheless produced significant high-energy gamma-ray emission, revealing rapid particle acceleration to hundreds of MeV.

Contribution

It presents detailed Fermi GBM and LAT data showing rapid acceleration of particles to >300 MeV within a few seconds during a modest solar flare.

Findings

High-energy gamma-ray emission lasted about 50 seconds.

Particles reached >300 MeV energies within 3-10 seconds.

Gamma-ray line fluence was unusually high for the flare class.

Abstract

The GOES M2-class solar flare, SOL2010-06-12T00:57, was modest in many respects yet exhibited remarkable acceleration of energetic particles. The flare produced an ~50 s impulsive burst of hard X- and \gamma-ray emission up to at least 400 MeV observed by the Fermi GBM and LAT experiments. The remarkably similar hard X-ray and high-energy \gamma-ray time profiles suggest that most of the particles were accelerated to energies >300 MeV with a delay of ~10 s from mildly relativistic electrons, but some reached these energies in as little as ~3 s. The \gamma-ray line fluence from this flare was about ten times higher than that typically observed from this modest GOES class of X-ray flare. There is no evidence for time-extended >100 MeV emission as has been found for other flares with high-energy \gamma rays.