Effect of Coulomb Collisions on the Particle Acceleration in Collapsing Magnetic Traps

The problem of particle acceleration in collapsing magnetic traps in the solar corona has been solved by taking into account the particle scattering and braking in the high-temperature plasma of solar flares. The Coulomb collisions are shown to be weak in traps with lifetimes t(l) < 10 s and strong for t(l) > 100 s. In the approximation of strong collisions, collapsing magnetic traps are capable of confining up to 20% of the injected particles in the corona for a long time. In the collisionless approximation, this value exceeds 90%. The question about the observational manifestations of collisions is examined. For collision times comparable to t(l), the electron spectrum at energies above 10 keV is shown to be a double-power-law one. Such spectra were found by the RHESSI satellite in flares.