The impact of ion-cyclotron wave dissipation on heating and accelerating the fast solar wind

Abstract

Using empirical ion velocity distributions derived from UVCS and SUMER ultraviolet spectroscopy, we construct theoretical models of the nonequilibrium plasma state of the polar solar corona. The primary energy deposition mechanism we investigate is the dissipation of high frequency (10-10000 Hz) ion-cyclotron resonant Alfven waves which can heat and accelerate ions differently depending on their charge and mass. We find that it is possible to explain many of the kinetic properties of the plasma with relatively small amplitudes for the resonant waves. There is evidence for steepening of the Alfven wave spectrum between the coronal base and the largest heights observed spectroscopically, and it is important to take Coulomb collisions into account to understand observations at the lowest heights. Because the ion-cyclotron wave dissipation is rapid, the extended heating seems to demand a constantly replenished population of waves over several solar radii. This indicates that the waves are probably generated throughout the wind rather than propagated up from the base of the corona.