Prototype Observations

Abstract

Measurements of radiation-belt particle fluxes often reveal temporal variations that are unaccompanied by comparable variations of the local geomagnetic field. These temporal variations definitely indicate violation of one or more of the adiabatic invariants. For example, following large enhancements in intensity above the mean level characteristic of a specific particle energy, drift shell, and pitch angle, particle fluxes often exhibit an approximately exponential decay, apparently caused by pitch-angle diffusion into the loss cone. (Pitch-angle diffusion violates the first and/or second adiabatic invariant.) Large depletions of flux (resulting from nonadiabatic processes that operate during sub-storms) often are erased in time by a diffusive exchange of trapped particles among drift shells. This latter process, known as radial diffusion can be identified with violation of the third invariant.