Um modelo não local para a emissão solar do tipo V

Abstract

There are several different radio emission phenomena that originate from the Sun and are related to the injection of energetic particles from the solar photosphere and chromosphere into the solar corona and the interplanetary medium. In this work, the Type V Solar Radio Emission is considered, assuming that the radiation is generated by the electron cyclotron maser mechanism. A model for the physical parameters of a source region located directly above an active region on the solar photosphere is employed, which is based in standard models and in recent observations taken by remote spacecraft. In order to enhance the efficiency of the cyclotron maser mechanism, the model assumes that a density cavity is formed in the source region, in such a way that the local plasma frequency is lower than the local cyclotron frequency. Using the magnetoionic theory of plasmas, the dispersion relation and the ray tracing equations are numerically solved for the slow extraordinary mode (Z mode) propagating inside the density cavity. Additionally, the emission coefficient for the Z mode is also obtained at each point along the ray’s path. Since the Z mode is trapped inside the coronal cavity, linear mode conversion from the Z mode to the Ordinary (O) mode is assumed, and at each point of the ray trajectory the Ellis window condition, which determines the position in the phase space where the conversion takes place, is verified. Once converted to the O mode, the radiation is allowed to propagate to the interplanetary space. Upon varying the values of the frequency of the radiation and the initial propagation angle, respective to the ambient magnetic field, the Z mode rays with a positive value of the emission coefficient at the starting point are followed in their trajectory until either the Ellis condition is satisfied or the wave is attenuated back into the background noise. The results indicate that the electron cyclotron maser is a viable mechanism for the generation of the Type V Solar Radio Emission.