Injection and loss of inner radiation belt protons during solar proton events and magnetic storms

Abstract

A survey of 27 to 45 MeV proton measurements from the HEO-3 satellite during the years 1998 through 2005 has been taken to describe variability in the outer part of the inner radiation belt and slot region (L = 2 to 3). Rapid (∼1-day) changes are described as injection or loss events, characterized respectively by Gaussian or exponential L dependencies. The radial extent of both event types is correlated to the minimum Dst of associated magnetic storms, while the injection magnitude is correlated to the flux of associated interplanetary solar proton events. Changes in the maximal L of observed trapped protons are consistent with trapping limits estimated from magnetic field line curvature. The inward extent and energy independence of the observed loss events are inconsistent with field line curvature induced scattering in a static magnetic field. However, time-dependent geomagnetic cutoff suppression, observed during magnetic storms, may be the cause of significant losses. Drift resonance with electric field impulses caused by rapid magnetospheric compression is the likely cause of both solar proton injections and radial shifts of preexisting trapped protons. © 2010 by the American Geophysical Union.