MAGNETIC SIGNATURES FOR SATELLITE ANOMALIES

Similarities have been found between the yearly trends of magnetic activity and the occurrences of electrostatic discharge events on a geosynchronous communication satellite from April 1983 to December 1987 in the declining portion of the 11-year solar cycle. The seasonal variations of magnetic activity and electrostatic discharge events show maxima around the equinoxes and minima during solstitial months. Detailed comparisons of the events with magnetograms from Yellowknife, Canada, near the footprint of the satellite, indicate that magnetic storms, substorms, and bays offer magnetic signatures for the discharge events with substorms playing a dominant role. A study of the occurrences of electrostatic discharge with respect to the magnetic perturbations indicates a variable time delay in the occurrence after the initiation of the magnetic disturbance. The local time variation pattern in the occurrence of electrostatic discharge shows preferred occurrences in the afternoon and evening sector. It is possible that a delay mechanism is operating, whereby the surface of the satellite is charged differentially in the midnight to dawn sector during substorm and discharged at some later time. It is also conceivable that the daytime anomalies are caused by buried charge processes. The occurrences of electrostatic discharge events in the traditional midnight to dawn sector and in the local time interval encompassing the Harang discontinuity appear to be immediate responses to the magnetic perturbations.