Geomagnetically Trapped Alpha Particles.

摘要

The present knowledge of the geomagnetically trapped alpha particles is reviewed in detail. The emphasis of the paper is on the most recent results. These recent studies show that the proton and alpha particle equatorial pitch-angle distributions are not the same. This gives rise to a (J sub alpha)/(J sub p) which is pitch angle dependent. Thus the (J sub alpha)/(J sub p) is about 0.01 at large equatorial pitch angles and about 0.001 to 0.0004 at small pitch angles for E/A > or = 0.5 MeV/nucleon. The recent studies of the temporal variations of low altitude alpha particles have shown that the particle intensity can increase by orders of magnitude in a few days. The alpha particle intensity then decays with an e-folding time of tens of days. The data are compared to theoretical predictions and several alternative explanations of the observations are offered.