On the origin of soft x-ray and microwave sources of emission in solar magnetic loops

Abstract

One possible mechanism is proposed for the appearance of high-temperature sources of emission in solar magnetic loops visible sometimes in the microwave and soft x-ray bands in active regions, even out of flares. The main concept of this mechanism is as follows. Due to the existence of current in the magnetic loop, there is a component of the electric field E‖ which is longitudinal to the magnetic field. In this case, at some heights the parameters of solar atmospheric plasma (density and temperature) appear to cause a certain number of electrons to be in a runaway regime. These electrons can be accelerated to energies of about 1–2 keV. This corresponds to the temperature of the observed microwave and x-ray source. Accelerated electrons satisfying the trapping condition will gradually fill the magnetic tube, and after a while a hot x-ray loop can occur. Similar mechanisms of the appearance of hightemperature sources of emissions in active regions probably take place in the simple loop flare for the class of thermal flares visible in the microwave and soft x-ray bands.