Numerical Calculation of the Lunar Wake in a Magnetohydrodynamic Model

Following previous interpretation, a model is developed which has the solar wind flowing directly into the lunar surface and the magnetic field passing unimpeded through the moon. The collapse of the plasma void behind the moon is calculated numerically using the equations of magnetohydrodynamics. The model is three-dimensional, allowing complete calculations to be made without special restrictions on the magnetic field direction. A cursory quantitative comparison with data shows agreement to be satisfactory. The calculations indicate that the rate of collapse of the void does not depend strongly on the solar wind-magnetic field angle. The penumbral decrease depends very strongly on both the solar wind-magnetic field angle and the angle of passage through the wake.