Stochastic heating and acceleration of minor ions by Alfvén waves

The present paper addresses the stochastic heating of minor ions by obliquely-propagating low-frequency Alfven waves in the solar wind. An important characteristics of the stochastic heating is unearthed by means of test particle simulation. That is, when the wave amplitude exceeds some threshold condition for stochasticity, the time-asymptotic kinetic temperature associated with the minor ions becomes independent of the wave amplitude, and it always approaches the value dictated by the Alfven speed, to wit, T-kin. similar to m(i)v(A)(2)/2. During the course of the heating process the minor ions gain a net average parallel speed, v(parallel to) similar to v(A) in the laboratory frame. These results are consistent with observations which find that minor heavy ions often move faster than the local protons with a speed roughly equal to the local Alfven speed. Citation: Wang, B., C. B. Wang, P. H. Yoon, and C. S. Wu (2011), Stochastic heating and acceleration of minor ions by Alfven waves, Geophys. Res. Lett., 38, L10103, doi:10.1029/2011GL047729.