Particle and field observations from Explorer 45 during the December 1971 magnetic storm period

The magnetic signatures of the extraterrestrial ring current have been measured by means of satellite-borne magnetometers on several occasions [Smith et al., 1960; Cahill, 1966; Coleman and Cummings, 1967; Sugiura et al., 1971]. In only one case have the charged particles of the magnetic storm-time extraterrestrial ring current system been directly observed [Frank, 1967]. In this note we present simultaneous observations from the S3-A (Explorer 45) satellite of the magnetic signature of the ring current and complete measurements of the proton ring current to distances of 5.24 RE during the double magnetic storm of December 16–19, 1971. Magnetic records from low-latitude and auroral magnetic observatories for this period have already been presented [Cahill, 1973].