On June 3, 2012, a very impulsive solar flare was observed by the GOES, RHESSI and FERMI-LAT satellites. The intensity of the flare was M3.3. The hard X-ray intensity (> 100 keV) rose ≥ 1000 times within one minute and then decayed immediately to the background level (in less than one minute). It was an extremely impulsive flare. By chance, the SEDA-FIB solar neutron detector onboard the International Space Station detected a 5.1σ enhancement due to solar neutrons. Therefore, it provided a good opportunity to investigate the mechanism of instantaneous proton acceleration to a few GeV. Based on the results of a new Monte Carlo calculation, we will show a reasonable proton acceleration model for the June 3, 2012 event. We also reexamined another very impulsive flare observed on June 10, 2010. PoS(ICRC2017)115 PoS(ICRC2017)115 Proton Acceleration by a Very Impulsive Flare K. Kamiya et al.
When the accelerated protons hit the solar surface, high-energy gamma-rays and neutrons are produced. However observed intensity of gamma-rays and neutrons at the Earth depends on not only the position of the flare on the solar surface but also the direction of the accerelated protons and helium ions. Without precise knowledge of the angular distribution of secondary particles, we cannot estimate correct intensity of accelerated ions. Therefore we have made a Monte Carlo simulation based on the GEANT 4 program to understand the angular distribution induced by the proton-solar atmosphere and the helium-solar atomosphere collisions.The collision processes of the accelerated ions with the solar atmosphere are simulated in the energy range of ions for Ep or He = 0.1-100 GeV. The intensity of secondary neutral particles such as gamma-rays and neutrons are calculated as a function of the energy and emission angle (θ) to the incident protons or helium ions. The results of the Monte Carlo calculation are compared with actual simultanious observation of neutrons and gammarays by the two detectors, being detected by the SEDA-FIB neutron detector on board the ISS and by the LAT high-energy gamma-ray detector on board the FERMI satellite. The secondary neutrons with energy of En ≥ 35 MeV and secondary gamma-rays with energy of Eγ ≥ 100 MeV are investigated for comparison with actual data of observation.
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