Simulation of a looptop hard X-ray source in turbulent plasma of solar flares

The kinetics of electron beams accelerated in the collisional plasma of solar (stellar) flares is considered, taking into account the stationary ion-acoustic mode localized at the magnetic looptop and magnetic fluctuations. The astrophysical aspect of the propagation process is related to the interpretation of hard X-rays in the plasma of flare loops. It is shown that when the plasma density in the coronal part of the solar flare loops does not exceed 10$^{10}$ cm$^{-3}$, taking into account the additional scattering on the ion-acoustic mode with the ratio of the turbulence energy density to the thermal energy of the plasma $\sim$ 5 $\times$ 10$^{-5}$–10$^{-3}$ and magnetic fluctuations with a level of 5 $\times$ 10$^{-2}$ does not lead to the appearance of a bright hard X-ray source in the coronal part of the loop in the model with the isotropic pitch-angle distribution of accelerated electrons. In the anisotropic case with a hard electron energy spectrum, the coronal hard X-ray source, in the presence of ion-acoustic turbulence, can exist for a short time after the beginning of turbulence generation. And only in the case of a soft energy spectrum of accelerated electrons (power spectrum index $>$ 5) and a relatively high plasma density at the magnetic looptop $>$ 10$^{10}$ cm$^{-3}$, a bright coronal hard X-ray source is generated at energies of 25–50 keV, regardless of the pitch-angular distribution of accelerated electrons at the moment of injection. A significant effect of turbulence on the distribution of the linear degree of hard X-ray polarization along the loop is shown, leading to a decrease in the extreme values in the coronal part by 5–35%. The integral values of the hard X-ray polarization do not exceed 10%.