A study of the mechanism of acceleration of 3He and heavy ions by Alfven turbulence in impulsive flares

Prompted by the observational result that in 3He-rich events the energetic 3He and heavy ions exhibit similar power-law distributions, we study by means of numerical solution of Fokker-Planck equation, the characteristics of the evolution of the distribution of ions after they are accelerated by Alfven turbulence. The results of computation show that the plasma density in the source region of acceleration and the energy density of Alfven turbulence play the chief role in the energy spectrum of the particles. For a plasma density n = (0.1–1)1010 cm−3, a magnetic field B = 50 – 100G and a turbulence energy density 0.4-2 ergs cm−3, the turbulent Alfven waves can accelerate 3He and heavy ions to the order of magnitude of 10 MeV/nucleon then in about 1 second. The index of the energy spectrum is 2.0–3.5. The result of the theoretical calculation basically agrees with the observation.