A Study of Accelerated Electrons in Solar Flares Using Microwave and X-Ray Observations

Abstract

We consider manifestations of accelerated electrons in microwave and hard X-ray emissions from solar flares. To meet our objectives, we discuss two events — those of 1999 March 16 and February 16. The first event is a short-duration burst, while the second is a long-duration event. An analysis of the first event leads to the conclusion that: 1) a seemingly single-loop configuration can actually be a double-loop one, and 2) it is possible that the pitch-angle distribution of the radio-emitting electrons can be anisotropic with practically no non-zero pitch angles. The second event shows seemingly intersecting flaring loops, and the formation of a post-eruptive arcade that can proceed as a series of double-loop interactions. From these and other published results, we conclude that: 1) double-loop configurations can be responsible for flares showing diverse morphologies and time profiles; 2) the pitch-angle distribution of accelerated electrons can be strongly anisotropic, with an excess of small angles, contributing to a rather narrow energy range of the microwave-emitting electrons.