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Title: How the IMF B-y induces a B-y component in the closed magnetosphere and how it leads to asymmetric currents and convection patterns in the two hemispheres
Authors: Tenfjord, P.
Østgaard, N.
Snekvik, K.
Laundal, K. M.
Reistad, J. P.
Haaland, S.
Milan, S. E.
First Published: 12-Nov-2015
Publisher: American Geophysical Union (AGU), Wiley
Citation: Journal of Geophysical Research: Space Physics, 2015, 120 (11), pp. 9368-9384 (17)
Abstract: We used the Lyon-Fedder-Mobarry global magnetohydrodynamics model to study the effects of the interplanetary magnetic field (IMF) By component on the coupling between the solar wind and magnetosphere-ionosphere system. When the IMF reconnects with the terrestrial magnetic field with IMF By≠0, flux transport is asymmetrically distributed between the two hemispheres. We describe how By is induced in the closed magnetosphere on both the dayside and nightside and present the governing equations. The magnetosphere imposes asymmetric forces on the ionosphere, and the effects on the ionospheric flow are characterized by distorted convection cell patterns, often referred to as “banana” and “orange” cell patterns. The flux asymmetrically added to the lobes results in a nonuniform induced By in the closed magnetosphere. By including the dynamics of the system, we introduce a mechanism that predicts asymmetric Birkeland currents at conjugate foot points. Asymmetric Birkeland currents are created as a consequence of y directed tension contained in the return flow. Associated with these currents, we expect fast localized ionospheric azimuthal flows present in one hemisphere but not necessarily in the other. We also present current density measurements from Active Magnetosphere and Planetary Electrodynamics Response Experiment that are consistent with this picture. We argue that the induced By produces asymmetrical Birkeland currents as a consequence of asymmetric stress balance between the hemispheres. Such an asymmetry will also lead to asymmetrical foot points and asymmetries in the azimuthal flow in the ionosphere. These phenomena should therefore be treated in a unified way.
DOI Link: 10.1002/2015JA021579
ISSN: 2169-9402
eISSN: 2169-9402
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: ©2015. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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