Impedance and large signal excitation of satellite-borne antennas in the ionosphere

The input impedance of a spacecraft-borne electric antenna operating below approximately 30 kHz in the ionosphere is investigated with emphasis on sheath effects. The impedance concept is generalized to be applicable to nonlinear antenna-magnetoplasma systems. Explicit formulas are obtained for the generalized impedance of a near cylindrical antenna taking into account the effects of large signal excitation, induced electromotive forces due to antenna motion across the Earth's magnetic field, the influence of the ion collection surface of the space vehicle, and of dc bias between antenna and vehicle. Comparison is made of the pertinent part of the theory and LOFTI-IIA satellite data.