The Coronas-F Space Mission pp 301-325
Protons Acceleration in Solar Flares: The Results of the Analysis of Gamma-emission and Neutrons Recorded by the SONG Instrument Onboard the CORONAS-F Satellite
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The SONG instrument onboard CORONAS-F satellite was the only experiment which observed neutral emissions with energies > 20 MeV from solar flares during the 23rd solar activity cycle. High-energy gamma emission was measured by SONG during four major flares, namely: August 25, 2001, October 28, 2003, November 04, 2003, and January 20, 2005. Spectra of this emission were restored in the energy range of 0.05–300 MeV and a broad line at energy range 40–100 MeV produced through π0-decay was distinguished. Generation of this line is a direct indication of the appearance of protons accelerated to energies above 300 MeV in the flare volume. In this way we determined the onset of high-energy proton acceleration. The same protons produce simultaneously high-energy neutrons which can leave the Sun. These neutrons were recorded by the SONG instrument after the flares of August 25, 2001, October 28, 2003, and November 04, 2003. Comparison of protons acceleration time during the October 28, 2003 and January 20, 2005 flares with the onset time of Ground Level Enhancement (GLE) leads to a conclusion that protons responsible for the GLE onset escaped from the solar atmosphere without any delay after their acceleration. The obtained results allow one to understand in a new way a process of particle acceleration up to relativistic energy during flare development.