Cape Town Anomaly and Auroral Emission

Abstract

IT has been recognized since the time of the Argus experiments^1,2 that the anomalously low value of the Earth's total magnetic field in the South Atlantic region must have a profound effect on the particles trapped in the radiation belts. The most convincing illustrations of this are the counting-rates of charged particles observed at relatively low altitudes with the Russian cosmic ships^3,4 and recent American satellites in the Discoverer series⁵. The maps prepared by both groups show two regions of high radiation intensity in the area of the South Atlantic Ocean, at heights of 250–500 km, where the counting-rates exceed those at corresponding geomagnetic latitudes elsewhere by factors of the order of 1,000 or more. One of these regions, coinciding well with the centre of the magnetic anomaly off the coast of Brazil, is attributed to the inner radiation belt. The other, referred to as the ‘south radiation anomaly’, lying between Cape Town and Antarctica, is thought to be due to the outer belt. These assignments are supported by the observation that the Argus belts of particles lay in the region between the two natural radiation belts¹, corresponding to the positions of the detonation sites between the two recently discovered anomalous radiation zones.