Hard X-ray bremsstrahlung emission and polarization in a flaring loop affected by electron beams

Abstract

Using a kinetic approach the hard X-ray bremsstrahlung emission and polarization produced by an electron beam injected, with an power law energy distribution from the corona into the chromosphere are investigated. The time-dependent kinetic equation was solved numerically in a flaring loop taking into account the energy losses and anisotropy of electron scattering for the following channels: Coulomb collisions and inelastic ones with neutral atoms, Ohmic dissipation and adiabatic scattering in a converging magnetic field. The temporal hard X-ray bremsstrahlung emission profiles are symmetric ones which resemble the observations for events with the timescale around a few seconds. The intensity of the X-ray bremsstrahlung emission increases and its directivity decreases with the time of a beam injection. The polarization is found to vary noticeably with the emergent photon energies below 40 keV being up to 30% and down to −10% for different angles of view. Harder X-ray polarization is almost constant with increase of photon energy, within a fixed angle of view.