Abstract

We consider the parametric instabilities of large-amplitude Alfven/ion-cyclotron waves and the consequent wave-particle interactions, and discuss their importance for modelling the evolution of ion velocity distribution fimctions in the tenuous and coUisionless plasma of a coronal hole and the fast solar wind. We perform ID hybrid simulations to study the nonlinear evolution of the parametric instabilities by analyzing the simulation results in terms of microinstabilities and discussing the influence of both Landau and cyclotron resonances on the evolution of the ion distributions. We demonstrate the origin of a relative drift between the protons and alpha particles, show the related anisotropic ion heating and follow the simultaneous proton beam formation. Finally, we focus on the development and evolution of both electromagnetic and acoustic microturbulence and present indications for an inverse energy cascade from shorter to longer wavelengths. © 2009 American Institute of Physics.