Model of high energy tail formation of ion distribution in turbulently heated plasmas

Ion heating or high energy ion tail formation due to an ion acoustic turbulence is considered using a model. The model requires the following assumptions; broad ion resonance, and the resonance region moving toward a higher velocity regime as time passes. A diffusion equation based on the above model is derived using the diffusion coefficient obtained by Dupree. The equation is analytically solved and under plausible assumptions it is found that the tail distribution is proportional to exp(-v/u0), u0 being the width of the resonance (the trapping velocity). The theory is compared with experiments and is found to explain qualitatively the results although the theory is one dimensional. (auth.)