  Most theoretical investigations of particle acceleration during solar flares
cannot be applied to observations for detailed study of the time evolution. We
propose a phenomenological model for turbulence evolution and stochastic
particle acceleration that links observations to the energy release and
particle acceleration through two coefficients characterizing particle
interactions with turbulent electromagnetic fields. In the linear regime the
particle distribution does not affect the turbulence energy cascade. It is
shown that electron acceleration critically depends on the intensity of
small-scale turbulence and an impulsive non-thermal component only appears near
the peak of the gradually evolving turbulence intensity. The model naturally
reproduces the soft-hard-soft pattern of hard X-ray pulses, and we attribute
the observed change in flux and spectral index correlation from the rise to
decay phase of some pulses to changes in the background plasma. Detailed
modeling of well-observed individual events will probe the energy release
processes.
