Distortion of the magnetosphere during a magnetic storm on September 30, 1961

A sudden commencement magnetic storm started on September 30, 1961. The Explorer 12 satellite was in orbit, in the day side of the magnetosphere, during the storm. During the recovery phase of the storm the field magnitude at 4 RE (earth radii), and at magnetic latitudes above 20°, was increased. A low-latitude pass, late in the recovery phase, revealed a field depression at 4 RE near the equator. The field distortions observed are attributed to inflation of the magnetosphere by low-energy charged particles on field lines from L = 2 to L = 5.