Preliminary Results of Magnetic Field Measurements in the Tail of the Geomagnetic Cavity

Abstract

A triaxial flux gate magnetometer was included in the Explorer 14 payload. This instrument was similar to the one carried on Explorer 12 (Cahill and Amazeen, 1963). The range of magnetic field measurement along each axis of the Explorer 14 magnetometer was nominally ±500 gammas. Explorer 14 was launched on 2 October 1962 into an elliptical orbit with apogee near 16 earth radii, inclination 33° and initial angle between the orbit major axis and the earth-sun line 70°. The initial spin rate of the satellite was 10 rpm. The satellite also had a precession motion of initial half-angle about 5°, this had decreased to 3° during the period 10–20 October. In November the precession cone opened up to 40° half-angle decreasing to 1° or less in early January 1963. To date we have analysed the magnetic data from a number of passes in October and in January when the precession cone was small. The October data are consistent with a geomagnetic cavity boundary, often beyond 16 earth radii, near 90° to the earth-sun line. Similar observations were obtained with Explorer 12 near the same region of the cavity one year earlier; Explorer 12 results indicated that the boundary was often beyond 12 earth radii.

Supported by NASA Contract NASw-155.