AN EXPLANATION FOR HUGE ENHANCEMENTS OF ULTRAHEAVY IONS IN SOLAR ~3HE-RICH EVENTS

摘要

Preferential heating and selective acceleration of oxygen (O) and ultraheavy ions (UH) with an atomic number Z> 34 in solar ~3He-rich or impulsive flares are theoretically and numerically investigated according to the two-stage acceleration mechanism. It is shown that parallel propagating ion-cyclotron Alfven waves can be much more efficient at heating ultraheavy ions than at heating oxygen through cyclotron resonances. This preferential heating of ultraheavy ions can result in three-order enhancements of abundance ratio UH/O in high-energy nuclei accelerated in the solar impulsive flares, which are consistent with the extreme enhancements of ultraheavy ions relative to oxygen observed in solar ~3He-rich events in recent years.