On the problem of power-law spectrum of particles accelerated in solar flares

The formation of power-law energy spectrum of particles accelerated in solar flares is investigated. The distinct difference between the mechanism and the model of acceleration is pointed out. It is shown that Fermi's model is described by linear differential equation of the first order and therefore a power-law spectrum is formed only for some special conditions which apparently are not fulfilled for flares. A satisfactory alternative to Fermi's model hasn't yet been found. In conclusion the connection between the mechanism of acceleration and a charge spectrum of accelerated particles is examined.