Average plasma-sheet configuration near 60 earth radii.

Nearly three years of Ames magnetometer data from Explorer 35 are used to establish plasma-sheet configurations in the geomagnetic tail at the lunar orbit. The plasma sheet is defined either as a region with different field orientations from normal magnetic-field directions in the tail, or as a region where the magnetic field variance is greater than elsewhere in the tail. The plasma-sheet configuration at the lunar orbit derived in this manner is found to be similar to the distribution at 18 earth radii observed by Vela satellites. The seasonal dependence and variations with geomagnetic activity are also presented.