Resonant Heating of Ions by Parallel Propagating Alfvén Waves in Solar Coronal Holes

Abstract

Resonant heating of H, O +5 , and Mg +9 by parallel propagating ion- cyclotron Alfven waves in solar coronal holes at a heliocentric distance is studied using the heating rate derived from the quasilinear theory. It is shown that the particle-Alfven-wave interaction is a significant microscopic process. The temper- atures of the ions are rapidly increased up to the observed order in only microsec- onds, which implies that simply inserting the quasilinear heating rate into the fluid/MHD energy equation to calculate the radial dependence of ion tempera- tures may cause errors as the time scales do not match. Different species ions are heated by Alfven waves with a power law spectrum in approximately a mass order. To heat O +5 over Mg +9 as measured by the Ultraviolet Coronagraph Spectrometer (UVCS) in the solar coronal hole at a region > 1.9R⊙, the energy density of Alfven waves with a frequency close to the O +5 -cyclotron frequency must be at least dou- ble of that at the Mg +9 -cyclotron frequency. With an appropriate wave-energy spectrum, the heating of H, O +5 and Mg +9 can be consistent with the UVCS