Source of Energetic Protons in the 2014 September 1 Sustained Gamma-ray Emission Event

Abstract

We report on the source of greater than 300 MeV protons during the SOL2014-09-01 sustained gamma-ray emission (SGRE) event based on multi-wavelength data from a wide array of space- and ground-based instruments. Based on the eruption geometry we provide concrete explanation for the spatially and temporally extended γ-ray emission from the eruption. We show that the associated flux rope is of low inclination (roughly oriented in the east-west direction), which enables the associated shock to extend to the frontside. We compare the centroid of the SGRE source with the location of the flux rope leg to infer that the high-energy protons must be precipitating between the flux rope leg and the shock front. The durations of the SOL2014-09-01 SGRE event and the type II radio burst agree with the linear relationship between these parameters obtained for other SGRE events with duration exceeding 3 hrs. The fluence spectrum of the SEP event is very hard, indicating the presence of high-energy (GeV) particles in this event. This is further confirmed by the presence of an energetic coronal mass ejection (CME) with a speed more than 2000 km/s, similar to those in ground level enhancement (GLE) events. The type II radio burst had emission components from metric to kilometric wavelengths as in events associated with GLE events. All these factors indicate that the high-energy particles from the shock were in sufficient numbers needed for the production of γ-rays via neutral pion decay.

39 pages, 14 figures, to appear in Solar Physics

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• First detection of >100 MeV gamma rays associated with a behind-the-limb solar flare
• The 2012 July 23 Backside Eruption: An Extreme Energetic Particle Event?
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Cited by in corpus (7)

• The coupling of an EUV coronal wave and ion acceleration in a Fermi-LAT behind-the-limb solar flare
• The Common Origin of High-energy Protons in Solar Energetic Particle Events and Sustained Gamma-ray Emission from the Sun
• Evidence for flare-accelerated particles in large scale loops in the behind-the-limb gamma-ray solar flare of September 29, 2022
• On the origin of hard X-ray emissions from the behind-the-limb flare on 2014 September 1
• The 2024 July 16 Solar Event: A Challenge To The Coronal Mass Ejection Origin Of Long-Duration Gamma-Ray Flares
• Relationship between solar energetic particle intensities and coronal mass ejection kinematics using STEREO/SECCHI field of view
• Role of CME clusters and CME-CME interactions in producing sustained $\gamma$-ray emission