HR: 14:45h
AN: SH52A-05    [PDF]
TI: HEO Observations of the Radiation Belt Electron Fluxes: Comparison with Model Predictions and a Source for Model Updates
AU: * Fennell, J F
EM: joseph.fennell@aero.org
AF: The Aerospace Corporation, P O Box 929957, Los Angeles, CA 90009 United States
AU: Blake, J B
AF: The Aerospace Corporation, P O Box 929957, Los Angeles, CA 90009 United States
AU: Heynderickx, D
AF: Belgian Institute for Space Aeronomy, 3 Avenue Circulaire, Brussels, B-1180 Belgium
AU: Crosby, N
AF: Belgian Institute for Space Aeronomy, 3 Avenue Circulaire, Brussels, B-1180 Belgium
AB: We have developed a database of energetic electron fluxes from observations taken by the HEO (94-026 and 97-068) satellites in the inner magnetosphere. The HEO satellites are in highly elliptical orbits, with orbital periods near 12 hours, that cover the L range 2 to 10 for HEO 97-068 and above 3.5 for HEO 94-026. HEO 97-068 covers the same L values at both high (above 2 Re geocentric) and low (below 1.2 Re geocentric) altitudes. Each satellite carries sensors that measure electron and proton fluxes over a wide range of energies. These data have been organized in B, L and MLT using the IGRF and Olsen-Pfizer field models. The database includes the total dose and dose rates observed behind several different shield thickness. The radiation dose measurements are compared to predictions from the current standard models (AE8 and AP8). One and four year average dose measurements indicate that the models over estimate the expected dose by significant factors, especially at shielding levels between 10 and 150 mils Al. The database has been used to study the dynamic response of the radiation belts to magnetic storms and for comparison with observations by other spacecraft. For example, we have compared the electron responses at the same L both at high and low altitudes as a check on the assertion that the radiation belt responses are coherent, i.e. the same at low altitudes as nearer the equator. In particular, we inter-compare the HEO 97-068 high and low altitude fluxes and the SAMPEX low altitude fluxes. We find that the high and low altitude fluxes do indeed track each other quite well with the low altitude 1.5 MeV electron fluxes being about 10 percent of the high altitude fluxes for L = 3 to 6, except during magnetic storm main phase. We have measured the flux decays that relate to the long-term losses following storm-time enhancements. As an example, at L = 3 the high-altitude 1.5 MeV electron fluxes were found to have three distinct 1/e decay times near 5, 10.5 and 17.5 days. These and other results obtained from the database will be presented, summarized and related to ongoing efforts to update the standard models.
DE: 2700 MAGNETOSPHERIC PHYSICS
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting