The radiation environment within the south Atlantic anomaly region and thecalculating trapped particles fluxes for low orbital satellite

The secular magnetic field variation in the south Atlantic anomaly (SAA) re gion is studied by using the international geomagnetic reference field (199 0s) model. Integral trapped particles fluxes along low altitude orbits and their secular variation are calculated with AP8/AE8 models. It is shown tha t below 1000 km at a fixed altitude above the SAA, the strength of magnetic field and trapped particles fluxes are decreased and increased with increa sing time, respectively, while higher than 1000km no noticeable variation a re found. We: think that the reason responsible for the secular variation o f particles fluxes is the distortion and "movement" of the drift shell. It is suggested that when calculating trapped particles fluxes at lower altitu des, one should use the contemporary IGRF model. Satellite observations mad e in the mid late 1980s seen to be consistent with the viewpoint of the pre sent work.