Effect of magnetic anomaly on particle radiation trapped in geomagnetic field

Anomalies in the geomagnetic field will affect the mirror altitude of trapped particles. A negative magnetic anomaly (abnormally weak magnetic field strength) will lower the mirror altitude of the trapped particles which are reflected near the anomaly. The large negative anomaly near Capetown, South Africa, will lower the local mirror altitude by about 1000 km. Since the trapped particles drift around the earth's magnetic axis, the outward projecting ‘horns’ in the contours of constant radiation intensity as revealed by Satellite 1958 ε may be explained on the basis of this anomaly and the east-west drift of the trapped particles. The gap in the radiation belt as revealed by Lunar Probe Pioneer III is also apparently related to this anomaly, and the intensity at the minimum relative to the adjoining maxima indicates that most of the trapped particles are reflected at relatively low altitudes.