Formation of magnetic anomalies antipodal to lunar impact basins: Two-dimensional model calculations

Journal Article · Mon Jun 10 00:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JB00308· OSTI ID:5256687

Hood, L L; Huang, Z ^[1]

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1. Univ. of Arizona, Tucson (United States)

The production of large-scale magnetic fields and associated crustal magnetization in lunar basin-forming impacts is investigated theoretically. Two-dimensional numerical models of the partially ionized vapor cloud produced in such impacts show that the low-density periphery of the cloud expands thermally around the Moon and converges near the antipode in a time of the order of 400 to 500 s for silicate impactor velocities of 15 to 20 km/s. Fields external to the impact plasma cloud are produced by the magnetohydrodynamic interaction of the cloud with ambient magnetic fields and plasmas. For the most typical case in which the Moon is immersed in the solar wind plasma and its embedded magnetic field, an MHD shock wave forms upstream of the cloud periphery separating the shocked solar wind from the free-stream solar wind. For impacts occurring on the downstream (antisunward) hemisphere, convergence of the impact plasma cloud and associated MHD shock waves occurs on the upstream side and results in a large antipodal field amplification. For impacts occurring on the upstream (sunward) hemisphere, some antipodal field amplification is still expected due to the finite electrical conductivity of the lunar interior (requiring an induced external magnetic field) and the likely presence of some residual plasma in the wake of the impact plasma cloud. During the period of compressed antipodal field amplification, seismic compressional waves from the impact converge at the antipode resulting in transient shock pressures that have been calculated to be as large as 2 GPa (20 kbar).

• OSTI ID: 5256687
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:B6; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MOON
MAGNETIC FIELDS
COLLISIONS
COMPRESSION
CRATERS
EVAPORATION
MAGNETIZATION
MAGNETOHYDRODYNAMICS
MATHEMATICAL MODELS
METEOROIDS
SEISMIC WAVES
SHOCK WAVES
SOLAR WIND
TRANSIENTS
TWO-DIMENSIONAL CALCULATIONS
CAVITIES
FLUID MECHANICS
HYDRODYNAMICS
MECHANICS
PHASE TRANSFORMATIONS
SATELLITES
SOLAR ACTIVITY
640107* - Astrophysics & Cosmology- Planetary Phenomena