The electrical conductivity of the Moon

Abstract

Abslxact. Investigations of the lunar electrical conductivity were described in excellent reviews by Sonett (1974) and Dyal et al. (1976). In this paper we will try to consider some new aspects of this problem in comparison with the Earth's data. Basic PrinciplesAs in the case of Earth induction, the EM-sounding of the Moon is based on Faraday's law. The main role in lunar excitation belongs to the TE-mode while the contribution of the TM-mode can be neglected due to very high resistivity of the near-surface dry lunar layer.The Moon has neither a magnetosphere nor an ionosphere with current systems. The only sources of induction are electrical currents in interplanetary plasma, running past the Moon like plane waves. If the solar wind velocity is as great as 10 a km/sec and magnetic fluctuations have periods about 102 sec, the wavelength reaches l0 s kin, i.e. some order to magnitude greater than the lunar radius. In this case one can consider this plane wave as a spatially homogeneous time harmonic magnetic field. Such a field can be described by the first spherical harmonic. However, if the solar wind velocity is only 150 km/sec and the period of fluctuations decreases to 10 sec, the wave lengths become shorter than the radius of the Moon. This corresponds approximately to the sixth-order spherical harmonic.Note, that the greater the harmonic number, the smaller the thickness of the layer which we can investigate. The greatest depth (not more than half a radius) can be investigated by using the first harmonic. Therefore one must try to use actually the first harmonic for lunar sounding. Unfortunately there is an additional cause which provides high harmonics, namely, the asymmetry of the lunar environment. Asymmetric Model of Electromagnetic Induction in the MoonDuring each revolution around the Earth the Moon crosses three different regions ( Figure 1).(1) The Earth's magnetic tail, where very low plasma density is observed.(2) Solar wind where plasma flows in the antisolar direction with the frozen-in magnetic field.(3) The magnetosheath which is the outer shell of the magnetosphere. In this area

Do Impulsive Solar-Energetic-Electron (SEE) Events Drive High-Voltage Charging Events on the Nightside of the Moon?

“…Figures 5, 6 and Table 28-1 of ITT (1977)). The interior lunar electrical conductivity is in the range of 10 −4 -10 −3 siemens/m (Sonett 1975;Vanyan, 1980), with a higher-conductivity lunar core (Hood et al, 1982).…”