Generation of X-Ray Spikes in Solar Flare Plasma

Measurements of hard X-ray emission ( E >20 keV) of solar flares on spacecrafts Solar Maximum Mission (SMM), Burst and Transient Source Experiment (BATSE), Konus–Wind, CORONAS, Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Fermi Gamma-ray Burst Monitor (Fermi GBM) indicate the presence of a complex time structure. Detailed temporal and spectral analysis of hard X-ray emission makes it possible to identify an ultrafine temporal structure consisting of a set of numerous pulses (hereinafter referred to as spikes) with a duration of less than 1 s. We calculate the hard X-Ray flux using a model of electron beam propagating in a flaring loop to compare it with the observed characteristics of the hard X-ray spikes for the different parameters of initial electrons beam, plasma and magnetic field at the time of injection. The temporal and spectral structures of the hard X-ray spikes and plasma parameters for a number of flares are analyzed. Their properties are determined, which serve as a criterion for selecting a numerical model with the specified characteristics of accelerated electrons—time profile, energy spectrum, pitch-angular distribution. In the events considered, the spike structure manifests itself more clearly at high energies. However, as follows from the simulation, the profiles of hard X-rays poorly reflect the pulse structure of the source on a scale of ~100 ms.