AN EMPIRICAL STATIC MODEL OF LOW-ENERGY RING CURRENT IONS

The empirical model consists of a set of average equatorial energy and pitch-angle distributions of fluxes of H+ and O+ in the energy range 110 eV to 35 keV for a number of local time and L ranges. It was constructed from data acquired by the Lockheed IMS-LO ion mass spectrometer on CRRES (apogee 6.3 R(E), inclination 18-degrees) which sampled a substantial portion of the ring current region. Equatorial distributions were constructed by mapping the ion data adiabatically from the satellite location to the equatorial plane, which was taken to be the minimum B surface. There the data were binned by their energy and equatorial pitch angle and sorted into ranges of L and local time. Equatorial distributions from many orbits were accumulated and averaged to construct the average equatorial distributions. This static model represents the average magnetosphere during the CRRES mission, August 1990 through October 1991, regardless of magnetic activity. In the absense of parallel electric fields and wave-particle interactions, the model may be used to estimate the ion distributions at non-equatorial magnetic latitudes by adiabatic mapping.