On cyclotron-wave resonance and ion velocity distributions in coronal holes and the fast solar wind

A scenario is suggested for coronal heating in which reconnection in the chromospheric network is assumed to create high-frequency waves. They are considered as the main energy source for the heating of the solar corona and generation of the fast solar wind. Multi-fluid models have been developed, which include on the basis of quasilinear theory (QLT) the damping of the waves. It is shown that a self-consistent treatment of wave damping and absorption is necessary. QLT predicts that ions in resonance with ion-cyclotron waves suffer merely pitch-angle diffusion. Evidence for this process is found in Hellos solar wind data. In the numerical results obtained from a semi-kinetic model for a coronal hole, the ion velocity distributions show also a "plateau", which is defined by a vanishing pitch-angle gradient at the resonance and implies marginal stability.