The role of electromagnetic ion-cyclotron waves in solar 3He-rich events

The preferential heating of He-3 by the electromagnetic ion-cyclotron waves, which propagate in the direction parallel to the magnetic fields in the solar corona, is investigated. The results obtained from this study indicate that the parallel propagating electromagnetic ion-cyclotron waves, if driven, can be efficient at heating He-3 through the first harmonic resonance. This preferential heating of He-3 can lead to a high temperature ratio T-3He/T-4He similar to 10-20 and thus largely increases the number of He-3 to be further accelerated to high energies. Comparing to the electrostatic ion-cyclotron waves, we find that the electromagnetic ion-cyclotron waves can be even more efficient at heating He-3 than the electrostatic ion-cyclotron waves if both types of waves are excited with comparable wave energy densities. Therefore, the electromagnetic ion-cyclotron waves, if generated in solar flares, should also play an important role in solar He-3-rich events along with the electrostatic ion-cyclotron waves. (C) 2013 Elsevier Ltd. All rights reserved.