3He-rich solar flares

A new subgroup of³He rich solar flares is found on reanalysing the global data.³He/H ratio as a function of maximum proton flux at an energy of about 10 MeV shows a break-up of the data into two groups. The first group follows the anticorrelation of³He/H ratio with the proton flux, as expected in the plasma process acceleration models. But the second group has a constant³He/H ratio as a function of maximum proton flux. This is not in conformity with the plasma process models. But this is expected in models where the nuclear spallation reactions are responsible for the production of³He. It is also found that the same break-up into two distinct groups follows if one plots the location of the flares in the solar disc. The first group is more or less confined to the west limb of the Sun, whereas the second group is more widely spread out across the solar disk. Visiting Professor, Tata Institute of Fundamental Research, Bombay, August–September, 1983.