1. Department of Physics, College of William and Mary, Williamsburg, Virginia 23185 (J.S.N.); Geophysics Directorate, Phillips Laboratory, Hanscom AFB, Massachusetts 01731 (M.H.); NASA Langley Research Center, Hampton, Virginia 23681 (R.S.R.); and Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529 (S.A.)