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Trapped Radiation ENvironment model Development

TREND-2

This studies covers different tasks.

Trapped radiation belt models based on the NASA models AP-8 and AE-8 and on data from Soviet satellites have been produced in the Soviet Union. The Soviet models have been evaluated and compared to the NASA models.

The UNIRAD software package has been extended and upgraded. A new external magnetic field model has been added and pitch angle dependence has been implemented. New trapped proton and electron models based on CRRES data have been added and new user interfaces have been written. The calculation of (B,L) coordinates has been hardwired into TREP to assure that the correct geomagnetic field models are used to access the trapped particle models. A study was made of the secular motion of the South Atlantic Anomaly and a correction for this effect was added to TREP.

A comprehensive and detailed description of the CRRES satellite, its payload and the data base formats has been compiled. The AZUR data base has been obtained from NSSDC.

The limitations of the (B,L) coordinate system at low altitudes already were noted in the previous TREND study. We found that a weighted average of the atmospheric density over a drift shell is much more effective to order trapped proton fluxes at low altitudes and may account for solar cycle variations of these fluxes. A program to calculate the density average, developed by A. Hassitt at UCSD, has been upgraded and extended. It has been applied to the flux distribution in the AP-8 models.

A statistical survey of the geostationary Meteosat-3 SEM-2 electron flux data was made. Average fluxes, energy spectra, anisotropies and flux level probabilities have been determined as a function of local time and geomagnetic activity indices. A wavelet analysis suggests a minimum repeat period of 3 hours for injection events.

The local time distribution of LANL geosynchronous electron fluxes and of electron data from the MEA and HEEF instruments on CRRES has been compared to the distribution of the Meteosat-3 SEM-2 electron measurements. There is good agreement between the HEEF and MEA data and between the MEA and SEM-2 data, but there are significant differences with the LANL data. The agreement between the MEA, HEEF and SEM-2 data marks them as valuable databases for new radiation belt models.

Electron pitch angle distributions were obtained from the MEA data. Different coordinate systems have been used to map the observed fluxes and their standard deviation. A new electron flux model in the (alpha0,L) coordinate system has been produced.

The geostationary GOES-7 energetic particle data were correlated with the Meteosat-3 SEM-2 electron data. Correlation coefficients between Kp and the GOES-7 electron flux have been determined. Periods of 27 and 13 days appear in the electron data, and a period of 22 days in the proton data. The GOES-7 data revealed that the SEM-2 electron flux at high energy contains a substorm component.

Project made under ESA/Contract No. 9828/92/NL/FM and a Rider