Observations of Storm-Time Ion Injection and Loss Processes in the Ring Current

Measurement of 20 keV ions pitch-angle distributions in the ring current during the magnetic storms of January 10,1997 and, May 15, 1997 show evidence of injection, pitch angle scattering and, precipitation. The observations were made with the IPS detectors of CEPPAD on the Polar spacecraft while intercepting the radiation belts at L-shells between 3 and 7 Earth radii, and at magnetic latitudes which span +/- 55 degrees. The magnetic local times (MLT) coverage of the Jan 10, 1997 measurements were confined to dawn and dusk. For the May15 storm the coverage was near noon and midnight. The progression of both storms was observed from onset through the main phase and early and late recovery phases. The main phase and early recovery of both storms exhibited elevated flux levels - indicating particle injection into the ring current over all L-shells. Very isotropic pitch-angle distributions were observed on the night side and at dusk local times, and over L-shells greater than 4, throughout main phase and early recovery - indicating strong pitch angle diffusion. In many cases these flat distributions extended over the loss cone regions - signifying enhanced precipitation. The observed enhanced precipitation, associated with strong diffusion into the loss cones at dusk and /or night local magnetic times, cannot be explained by recent modeling efforts that incorporate wave particle interaction scattering losses. Instead this precipitation has the signature of current sheet scattering of ions associated with distortions of the near geomagnetic tail, that cause a violation of the Measurement of 20 keV ions pitch-angle distributions in the ring current during the magnetic storms of January 10,1997 and, May 15, 1997 show evidence of injection, pitch angle scattering and, precipitation. The observations were made with the IPS detectors of CEPPAD on the Polar spacecraft while intercepting the radiation belts at L-shells between 3 and 7 Earth radii, and at magnetic latitudes which span +/- 55 degrees. The magnetic local times (MLT) coverage of the Jan 10, 1997 measurements were confined to dawn and dusk. For the May15 storm the coverage was near noon and midnight. The progression of both storms was observed from onset through the main phase and early and late recovery phases. The main phase and early recovery of both storms exhibited elevated flux levels - indicating particle injection into the ring current over all L-shells. Very isotropic pitch-angle distributions were observed on the night side and at dusk local times, and over L-shells greater than 4, throughout main phase and early recovery - indicating strong pitch angle diffusion. In many cases these flat distributions extended over the loss cone regions - signifying enhanced precipitation. The observed enhanced precipitation, associated with strong diffusion into the loss cones at dusk and /or night local magnetic times, cannot be explained by recent modeling efforts that incorporate wave particle interaction scattering losses. Instead this precipitation has the signature of current sheet scattering of ions associated with distortions of the near geomagnetic tail, that cause a violation guiding center approximation