The magnetic moment of model ring current belts and the cutoff rigidity of solar protons

The magnetic moment M/sub R/ of the ring current is calculated for model ring current belts, together with their magnetic fields along an equatorial radius. A graph shows the relation between the ratio M/sub R//M/sub E/(M/sub E/ = the magnetic moment of the earth) and the intensity DELTA H of the ring current field at the equator on the earth's surface. It gives possible ranges of the ratio M/sub R//M/sub E/ for observed values of DELTA H and approximate upper limits of both M/sub R//M/sub E/ and DELTA H for each belt. On the basis of diagram, the entry of low-energy solar protons is discussed, and it is shown that the ring current alone cannot produce the drastic reductions of apparent cutoff rigidity of solar protons observed by detectors carried by balloons and satellites. (auth)