A source of solar protons: The temperature of flare plasma and injection moments

Abstract

The relationship between injection moments of solar protons of ∼100 MeV in the heliosphere and the temperature of flare plasma in six long events of the 23d cycle is considered. Injection moments are evaluated by the arrival time of first protons to an observer in the ecliptic plane (GOES), and the temperature is assessed by the ratio of X-ray intensities in two energy channels of GOES. The temperature of the flare plasma depends on the efficiency of heating (the spectrum of accelerated electrons and properties of the target) and cooling. Time profiles of gamma radiation and moments of particle injection into the heliosphere in the ecliptic plane indicate that the acceleration of particles with the most rigid spectrum can occur under different physical conditions, i.e., during a temperature increase or decline. The phase of a temperature decline corresponds to the increase in the altitude of the acceleration region (for a coronal source) and a reduction in plasma density. At this time, the intensity of gamma radiation is usually below the threshold of modern detectors.