In some solar flares, the abundance of ³He ions with energy of the order of MeV/n is extremely increased. As a mechanism for the ³He rich events, current-driven instabilities are believed to be important, and several theoretical models based on the linear stability theory have been proposed. However, these models have not succeeded in explaining the observations quantitatively.
In order to solve this problem, we study nonlinear development of the current-driven instabilities and associated energy transport in a multi-ion-species plasma, by means of a two-dimensional, electrostatic, particle code [1]. It is shown that the H cyclotron waves with frequency near 2 Ω_3He eventually become dominant through the change in the electron velocity distribution function (Here, Ω_3He is the cyclotron frequency of ³He ions). These waves selectively accelerate ³He ions. The maximum energy of ³He ions increases with the initial electron drift energy.
We have also developed a theory predicting the dominant waves and the maximum ³He energy accelerated by these waves. This theory predicts that if the initial electron energy is of the order of 10 keV, many ³He ions with the energy of the order of MeV/n would be produced. This agrees with the observations that the ³He rich events are almost always accompanied by energetic electrons with 1-100 keV [2].

References