Fermi Large Area Telescope observations of high-energy gamma-ray emission from behind-the-limb solar flares

TL;DR

Fermi-LAT observations have significantly increased detected high-energy solar flares, including the first >100 MeV gamma-ray emissions from behind-the-limb flares, providing new insights into particle acceleration.

Contribution

This study reports the first detection of >100 MeV gamma-ray emission from behind-the-limb solar flares, expanding understanding of solar flare emissions and acceleration mechanisms.

Findings

First >100 MeV gamma-ray detection from occulted flares

Increased detection rate of high-energy solar flares

Insights into particle acceleration in solar flares

Abstract

Fermi-LAT >30 MeV observations have increased the number of detected solar flares by almost a factor of 10 with respect to previous space observations. These sample both the impulsive and long duration phases of GOES M and X class flares. Of particular interest is the recent detections of three solar flares whose position behind the limb was confirmed by the STEREO-B spacecraft. While gamma-ray emission up to tens of MeV resulting from proton interactions has been detected before from occulted solar flares, the significance of these particular events lies in the fact that these are the first detections of >100 MeV gamma-ray emission from footpoint-occulted flares. We will present the Fermi-LAT, RHESSI and STEREO observations of these flares and discuss the various emission scenarios for these sources and implications for the particle acceleration mechanisms.