Quiet‐time electron precipitation at L = 4 in the South Atlantic Anomaly

Abstract

On January 12, 1978, at 1000 UT, a Superarcas sounding rocket was launched from Siple Station, Antarctica, (L = 4.1, 76°S, 84°W) during a prolonged geomagnetically quiet period (Kp = 1+) with very low VLF activity. The parachuted payload observed a moderately intense charged particle flux that smoothly decreased as the payload descended through the atmosphere. These data have been carefully extrapolated to zero depth in the atmosphere for comparison with both low‐altitude satellite measurements and theoretical predictions of the precipitating flux in the region of the South Atlantic anomaly. The integrated flux was found to agree reasonably well with both the satellite measurements and prediction. The calculated spectrum was found to be much softer than typical trapped electron spectra reported from satellite measurements after extended periods of low magnetic activity. This result is consistent with experimental observations that the lifetime of outer belt particles increases with energy.