Microwave solar flare spectra of complex magnetic ambient

Abstract

The magnetic field lines were never so depicted as in the recent results about active regions on the sun from the EUV experiments on board of SOHO and TRACE satellites. The main result is a clear complexity of the, as called, magnetic arcs on top of the sunspots with arc second spatial resolution of the field lines connecting different magnetic polarities. The microwave solar bursts occurring in this magnetic ambient have been treated, in most of analysis, as a homogeneous source of gyrosynchrotron emission. We developed a numerical code for the emission, self‐absorption and transfer equation of the ordinary and extraordinary modes for this complex ambient to calculate the flux density map and spectrum of the emitting region. We applied our code for a non‐thermal distribution of electrons, with number density typical for solar flares, with anisotropic pitch angle distribution, a hydrostatic ambient density and analyzed the spectrum for many viewing angles. For the magnetic field configuration we idealized a complex array of magnetic arcs simulating one of these observed scenarios for our first result presented here. The code is also prepared to use a non‐linear extrapolation of photospheric magnetic field. Our main concern in this analysis was to show some of the geometric dependence of the spectrum shape as an alternative for the general interpretation based on a composition of many isotropic sources with distinct magnetic field or bremsstrahlung competition to broad and/or reinforce the emission in specific frequency bands.