Nighttime observations of 0.2‐ to 26‐keV electrons in the South Atlantic Anomaly made by Atmosphere Explorer C

Abstract

The high‐energy background radiation in the South Atlantic Anomaly makes it difficult to measure the fluxes and spectra of the low‐energy particles with any degree of certainty, and as a result no values for the energy range below 30 keV are to be found in the literature. We have found that the flux of low‐energy ions is much smaller than that of the electrons. This has enabled us to use the low‐energy ion detector on AE‐C to monitor the high‐energy background and to correct the response of the low‐energy electron detector for this. The electron spectra can be represented by a power law in the range 0.2–26 keV, with the spectral index close to −1. Maps are shown of downward energy flux in this range over the South Atlantic Anomaly. The mean energy flux carried by electrons in the middle of the anomaly is found to be about 3 × 10−3 erg cm−2 s−1 and may reach 5 times this value on occasions. A surprising result is that this energy flux decreases as Kp increases.