Plasma waves radiated by a moving conducting body between successive gyrofrequencies

Abstract

We present the solutions of a theoretical analysis of the magnetic field wake of a conducting body in a flowing plasma when the Hall current is dominant in the waves. The results show a wake swept back in the flow, the front of which is a straight line determined by the group velocity of the waves excited by the current source. Characteristic directions of constant phase of the field variables are found to lie upon a series of parabolas rather than the single, straight magnetohydrodynamic characteristics. We also find modulation along the characteristics with a wavelength proportional to the size of the conducting obstacle. Magnetic field lines supporting wave activity exhibit a helical structure of decreasing pitch away from the source. The current carried by the waves and the wave power are largest along the leading edge of the wake, in the high‐frequency components of the waves. Our results are of relevance to electrodynamic coupling between a conducting satellite and its associated planetary magnetosphere in a multi‐ion plasma, as found in the environments of the gas giants. The solutions are also applicable to the whistler wave dispersion relation, and we find a good agreement with simulation results based on suggested “whistler wings” generated at the asteroid Gaspra.