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Thayer School of Engineering

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Department of Physics and Astronomy


Abstract: The distribution of high-speed plasma flows measured at radial distances of 10-30 RE in the neutral sheet of Earths magnetotail is highly skewed toward the premidnight sector. This pre/postmidnight asymmetry has been observed by many spacecraft, yet its causes remain unknown. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. We show using global numerical simulations that the electrodynamic interaction between Earths magnetosphere and ionosphere produces an asymmetry consistent with observed distributions in nightside reconnection and plasma sheet flows and in accompanying ionospheric convection. The primary causal agent is the meridional gradient in the ionospheric Hall conductance which, through the Cowling effect, regulates the electrical load characteristics of the ionosphere and the distribution of electrical currents flowing between it and magnetohydrodynamic dynamos in the magnetotail.\r\nOne Sentence Summary: Geospace simulation experiments show that magnetosphere ionosphere coupling regulates the distribution of magnetic reconnection in Earths magnetotail.