The production and evolution of plasma and associated magnetic fields during hypervelocity impacts: Implications for planetary paleomagnetism

Details The production and evolution of plasma and associated magnetic fields during hypervelocity impacts: Implications for planetary paleomagnetism The production and evolution of plasma and associated magnetic fields during hypervelocity impacts: Implications for planetary paleomagnetism

Jan 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........26c&link_type=abstract

Ph.D. Thesis Brown Univ., Providence, RI.

Physics

Dynamo Theory, Hypervelocity Impact, Lunar Magnetic Fields, Lunar Surface, Magnetic Cores, Meteorite Collisions, Lunar Evolution, Magnetic Properties, Paleomagnetism, Plasmas (Physics)

Scientific paper

Magnetic fields generated within plasma produced by hypervelocity meteoroid impacts were proposed to explain the remanent magnetism of some lunar samples as well as broad areas of the lunar surface. The origin of the lunar remanent fields may be due to crustal remanence of a core dynamo field occurring early in lunar history prior to extensive modification by impact or remanence of transient fields, particularly associated with impacts, occurring on a local scale throughout lunar history. The presence of an early core dynamo field would have strong consequences for the formation and early evolution of the Moon, yet to deconvolve the role that an internally generated core dynamo field may have had, it is necessary to understand the important role that impact-induced magnetization may have on the magnetic state of the lunar surface. The production and evolution of plasma and associated magnetic fields during hypervelocity impacts through an iterative experimental and theoretical approach is addressed. The configuration and duration of spontaneous impact-generated magnetic field observed in the laboratory are dependent on projectile and target composition and have a strong dependence on impact angle. Self-similar, one-dimensional solutions for the evolution of the magnetic field within impact-generated plasma demonstrate that peak magnetic field strength probably increases with increasing crater size at the same diameter-scaled distance. Magnetic fields produced by highly oblique (less than 15 deg -30 deg from horizontal) impacts are particularly enhanced. Impact-generated magnetic fields, extrapolated from experimental data, are likely to be large enough to account for the magnetization of certain relatively young (less than 3 Ma-1.5 Ga) lunar sample and may help account for the lunar magnetic record during the last approximately 3.6 billion years. More generally, crater-related paleomagnetic fields on solid surface bodies in the solar system may be general compositional indicators (e.g. asteroidal vs. cometary impacts) and may yield a diagnostic signature of impact angle where other clues (shape, eject a pattern) are absent or ambiguous.

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