Some effects of diamagnetic ring currents on Van Allen radiation

The distortion of the geomagnetic field by diamagnetic ring currents (such as the magnetic storm main phase ring current) is calculated quantitatively. It is shown that these distortions cause changes in the energy of the trapped electrons in the outer zone of the Van Allen radiation belt. The changes are brought about by betatron acceleration and deceleration of the trapped radiation as the distortions move the radiation from one field strength region into another. A model is presented involving a system of two diamagnetic ring currents for which there is some observational evidence. In this model part of the geomagnetic storm energy is temporarily transferred to the Van Allen radiation. It is proposed that such a mechanism contributes, in part, to the major fluctuations in the observed intensities of the outer zone of the radiation belt because (1) the changes in particle energy cause changes in the counting rate of radiation instruments flown through the belt, and (2) the Van Allen electron number density is a steep function of radial distance so that distortions of the geomagnetic field can cause changes in particle flux. (auth)