Ionospheric Effects on the Paleomagnetosphere

Details Ionospheric Effects on the Paleomagnetosphere Ionospheric Effects on the Paleomagnetosphere

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufmsm11b..01z&link_type=abstract

American Geophysical Union, Fall Meeting 2003, abstract #SM11B-01

Physics

1535 Reversals (Process, Timescale, Magnetostratigraphy), 2411 Electric Fields (2712), 2708 Current Systems (2409), 2736 Magnetosphere/Ionosphere Interactions, 2760 Plasma Convection

Scientific paper

Paleomagnetic studies indicate that the strength of the Earth's internal magnetic field has varied over the range 0.1 to 3 of the present value. Consequently the paleomagnetosphere, which results from the coupled interaction of the solar wind, the Earth's internal magnetic field and the conductive paleoionosphere, must have undergone severe changes, especially during the so-called polarity transition epochs, when the Earth's internal dipole moment reversed. Different transition scenarios can be conceived, none of which is excluded in the present state of our knowledge: The dipole moment could decay to zero and quickly build up again in the opposite direction; or a much reduced dipole moment could turn around, staying close to the equatorial plain for a significant time; or the dipole moment could completely vanish and higher order multipoles could dominate during the transition epoch. In a paleomagnetosphere with reduced internal magnetic field the ionospheric conductivity is expected to be higher, which implies stronger ionosphere-magnetosphere coupling, i.e. stronger ionospheric and field aligned magnetospheric currents. Although several scaling relations have been found to scale different parameters of a dipolar paleomagnetosphere to the dipole moment, no theoretical scaling relations exist for the magnetospheric-ionospheric current systems that control the inner magnetospheric convection. In the first part of this paper, we present some theoretical considerations and new scaling relations related to the current systems in the paleomagnetosphere. In the second part, we test the effect of different ionospheric boundary conditions and conductivity models on different types of paleomagnetospheres by means of the Michigan BATS-R-US MHD code. Namely, we study the inner magnetospheric plasma convection patterns and the equivalent ionospheric electric potential patterns. In general, we conclude that the ionosphere plays a more important role in the paleomagnetosphere during polarity transition epochs.

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