Note on dispersive Alfven waves in the solar corona

Abstract

The dispersive (kinetic) Alfven waves in the ion-cyclotron frequency regime (ICKAWs), with frequencies close to the ion cyclotron frequency and with wavelengths close to the ion gyroradius, are studied in view of their ability to interact strongly with the plasma of solar corona. The combined action of finite ion cyclotron frequency and finite ion gyroradius effects has a profound influence on the Alfven wave. The phase velocity of ICKAWs along the background magnetic field can be slower than the Alfven velocity (due to finite ion cyclotron frequency effects), but also faster than the Alfven velocity (due to finite ion gyroradius effects). The phase velocity depends on both the perpendicular and parallel wavenumbers, and spans a range of velocities from sub-Alfvenic to super-Alfvenic. Since these waves have a field-aligned component of electric field, they undergo Cherenkov resonant interaction and can be excited by the ion beam component set up in the low corona by the reconnection outflows from chromosp...