Penetrating Radiation Environment and Effects Study.

Abstract : This report summarizes some of the PREE achievements to data on data acquired from the Lockheed IMS-HI and SEP instruments on the CRRES satellite. The primary objectives of the PREE research are to: (1) inter-calibrate the ONR 307 instruments; (2) develop algorithms and software for understanding and modeling the radiation belts; (3) develop key parameters; and, (4) study the dynamic radiation belt variations in the slot region and the outer belt. The new IMS-HI instrument performed well during the CRRES mission and has been inter- calibrated with the IMS-LO, SEP and EPAS instruments. Much progress has been made in the development of key algorithms and software for mapping the electron, ion, and neutral flux. Energetic neutrals from the ring current have been observed directly and are an important low altitude and low latitude ionization source. Surveys of the medium energy (20-1000 keV) ion and neutral database indicate a sharp edge to the ring current flux which is not apparent in previous studies. The neutral flux is linked strongly with the low altitude edge of the ring current. To properly map the radiation belts and select key parameters a simple physical model was developed for the response of the magnetosphere to magnetic storms. The CRRES data indicate that the radiation belts including the inner belt are strongly modified during a sudden commencement (SC) on the order of several minutes. This momentary compression results in a net acceleration and transport of particles to low L in violation of the third invariant. For the 24 March 1991 magnetic storm the magnetopause is inferred to have penetrated to L approximately 3.0 resulting in the possible establishment of the 'new inner belt'.