ELF observations during the December 1971 storm.

Initial results from the University of Minnesota search coil magnetometers aboard the Explorer 45 Satellite show several types of ELF signals during the magnetic storms of Dec. 16-19, 1971. The orbit of the satellite at this time was nearly equatorial, with an apogee near 5 earth radii at 2100 local time, and a perigee below 300 km. The emissions vary during different phases of the storms and also with the position of the spacecraft in the magnetosphere. The location of the plasmapause appears to be a particularly important factor in determining the type and intensity of the signals.