Particle interactions with single or multiple 3D solar reconnecting current sheets

The acceleration of charged particles (electrons and protons) in flaring solar active regions is analyzed by numerical experiments. The acceleration is modelled as a stochastic process taking place by the interaction of the particles with local magnetic reconnection sites via multiple steps. Two types of local reconnecting topologies are studied: the Harris-type and the X-point. A formula for the maximum kinetic energy gain in a Harris-type current sheet, found in a previous work of ours, fits well the numerical data for a single step of the process. A generalization is then given approximating the kinetic energy gain through an X-point. In the case of the multiple step process, in both topologies the particles' kinetic energy distribution is found to acquire a practically invariant form after a small number of steps. This tendency is interpreted theoretically. Other characteristics of the acceleration process are given, such as the mean acceleration time and the pitch angle distributions of the particles.Comment: 18 pages, 9 figures, Solar Physics, in pres

Plasma Diagnostics of the Interstellar Medium with Radio Astronomy

Contains fulltext : 119335.pdf (preprint version ) (Open Access

Comparison of the energy spectra and number fluxes from a simple flare model to observations

In this paper, we investigate the energy spectra produced by a simple test particle X-point model of a solar flare for different configurations of the initial electromagnetic field. We find that once the reconnection electric field is larger than 1 Vm⁻¹ the particle distribution transits from a heated one to a partially accelerated one. As we close the separatrices of the X-point and the angle in the inflow direction widens we find that more particles are accelerated out of the thermal distribution and this power-law component extends to lower energies. When we introduce a guiding magnetic field component we find that more particles are energised, but only up to a maximum energy dictated primarily by the reconnection electric field. Despite being able to accelerate particles to observable energies and demonstrate behaviour in the energy spectra that is consistent with observations, this single X-line model can only deliver the number fluxes required for microflares