Magnetic `fossils’ from Mercury, and the other terrestrial planets and moons

Michael PURUCKER, NASA Goddard Space Flight Center, USA | 27 septembre 2012

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We determine minimum and maximum limits for the presence of a fossil remanent magnetization in Mercury’s crust, based on an approach which first models and removes fields from Mercury’s offset dipole, it’s magnetopause, cross-tail current, and cusp, and near-planet fields of external origin but unknown provenance. The minimum field of crustal origin is 11 nT at 300 km altitude, and it is spatially coincident with, or closely associated with, the northern rise within the Northern volcanic province. This magnetic field is deduced from both radial and theta components of the observation, and the two components are consistent. The field magnitude, and the deduced magnetization, is significantly smaller than that measured at Earth, but larger than fields measured at Earth’s moon. The direction of the remanent field is in the opposite sense to the present main field direction, implying field reversals in the past.

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