Radial diffusion of starfish electrons

Abstract

A study of the change in electron intensities in the Starfish electron belt from January 1, 1963, to November 3, 1965, indicates that radial diffusion, both inward and outward from L of 1.40, was a significant loss mechanism for these electrons during this period. For L values of 1.20 and below, the indicated steepening of the pitch-angle distributions during this period has been interpreted as the result of a radial diffusion source for each L shell concentrated near the geomagnetic equator. Since pitch-angle diffusion lifetimes are not well known for 1.20 < L < 1.65, a definitive radial diffusion coefficient cannot be computed from these data. A maximum reasonable diffusion coefficient (mean square displacement per unit time) computed for this range of L for this period has a minimum at L of 1.31, and a value of 4.4 × 10−5 RE²/day at that point. This maximum coefficient, representing an average over a 3-year period, is more than an order of magnitude too small to account for the apparent radial diffusion of natural electrons into this region that took place in September 1966. The results are, however, consistent with population of the inner zone by radial electron diffusion occurring during relatively short periods during which the diffusion coefficient is enhanced by two or three orders of magnitude.