Year: 1973
Type: article
Abstract: The electromagnetic response of the moon to excitation by the time-dependent fluctuations of the interplanetary magnetic field is given for the dark or antisolar hemisphere of the moon. Six hours of time series data from the Explorer 35 Ames magnetometer and the lunar surface magnetometer on Apollo 12 are used to obtain the Fourier spectral amplitudes of the surface and interplanetary fields from which transfer functions are calculated for the east-west, north-south, and vertical directions at the Apollo site in the bandwidth 1.7 × 10−3 ≤ ƒ ≤ 3 × 10−2 Hz. The tangential magnetic field on the night side hemisphere is amplified by confinement within the diamagnetic cavity and redistribution of magnetic field lines from the sunlit to the night side. Vacuum scattering from even a perfectly conducting moon cannot produce the observed night side tangential magnetic field amplification. The night side electromagnetic behavior of the moon is not that of a body in vacuum. A critical discussion of lunar conductivity profiles derived from night side radial magnetic field data and vacuum scattering theory is presented. Limitations imposed by the quantity and the frequency range of the data and the necessity to account for contributions from cavity confinement and internal redistribution of field lines to the night side radial field make heretofore derived night side conductivity profiles unreliable. In particular, we show that there is no evidence for a lunar core as conducting as 10−2 mho/m. Inversion of night side radial magnetic field data should await the development of a time-dependent asymmetric theory of lunar magnetic induction.
Authors: G. Schubert, B. F. Smith, C. P. Sonett, D. S. Colburn, K. Schwartz
Institutions: University of California, Los Angeles, Ames Research Center
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2081070754