Proton acceleration by very impulsive flare on June 3, 2012

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.