Loss and replenishment of electrons at middle latitudes and highBvalues

Using data from the satellite 1963 38C, we have measured the spatial characteristics of electrons trapped at high B values in the region 1.4 ≤ L ≤ 3.4. The data were obtained from an integral electron spectrometer sensitive to electrons of eneregy Ee ≥ 280 kev, ≥ 1.2 Mev, ≥ 2.4 Mev, and ≥ 3.6 Mev. An intense peak of electrons at Ee ≥ 280 kev and a corresponding lack of high energy (Ee ≥ 1.2 Mev) electrons were observed at L ∼ 2.5. Fluxes of 1.5(10)6 electrons (Ee ≥ 280 kev)/cm2 sec ster were observed. A longitude dependence of the observed electron intensity was measured, and plots of the fractional electron transmission through the South Atlantic anomaly were obtained as a function of B value on various L shells. It was found that electrons mirroring at B values which remain above ∼350 km in altitude over the South Atlantic anomaly are not disturbed by the anomaly; about 90% of those that reach the 100- to 250-km region over the anomaly are lost, and all those electrons reaching an altitude of ≤100 km over the anomaly are lost. The data indicate that particles are injected into the depleted regions at all longitudes, and that the resulting longitudinal intensity distribution is quite stable during magnetically quiet periods. The data further suggest that the loss of electrons in the anomaly and their subsequent replenishment is a general effect, occurring throughout the radiation cavity.