Particle acceleration in the current layer of solar flares

The applicability and effectiveness of the main mechanisms of particle acceleration under the real conditions of solar flares (more strictly, their turbulent current sheets in which the flares release their energy) are analyzed. It has been shown that the realization of the mechanisms of pure regular acceleration by the electric field (disregarding the particle-plasmon electric scatterings) and pure stochastic acceleration in the turbulence field (disregarding the regular electric field) faces the difficulties of principle in both the theoretical treatment and the comparison with observatons. The mechanism of ''quasidiffusive'' acceleration including the processes of both types is proposed. In this case, the particle energy increases during the spatial diffusion of the particle in the electron field. In its turn, the diffusion is due to the high frequency of the particle-plasmon elastic collisions. It has been shown that this mechanism is most effective under the conditions of solar flares. The calculations of the equilibrium energy spectrum incuding the thermodiffusion and three-dimentionality of the sheet give the power spectrum of the form eta sup(*) sub(epsilon) approximately epsilon -sup(γ) with α approximately 3. The high-energy cut-off of the spectrum and the chemical composition of the accelerated particles are examined. (author)