Diagnostics of the region of nuclear interactions of neutrons in the solar flare of January 20, 2005 by gamma-ray lines

Based on an analysis of the time history of the count rate in the 2.223 MeV neutron-capture line from the extreme solar event of January 20, 2005, we investigate the density of the surrounding medium and the $^3$He content in the area of the 2.223 MeV gamma-line production. The analysis uses data on count rates in the 2.223 MeV gamma-ray line, as well as in lines ranging from 4 to 7 MeV, which were acquired with the AVS-F apparatus from the SONG-D detector onboard the CORONAS-F satellite. It is shown that simulation of the time history of the 2.223 MeV gamma-ray line from the flare event would require an assumption of the elevated abundance of $^3$He. It is found that in the area of the 2.223 MeV gamma-line production the ratio $n(^3\mbox{He})/n(^1\mbox{H})$ is (${(1.4\pm0.15)\cdot10^{-4}}$, although, based on the data from different flares, on average it is approximately ${2\cdot10^{-5}}$. The elevated abundance of 3He may be considered as an additional indirect argument for the possible presence of reaction products of neutron radiative absorption by the $^3$Не isotope within a small increase in gamma emission in the 15–21 MeV range over the background level (which was detected previously from the CORONAS-F/AVS-F data).