Space Physics Seminar fall-2015

Impact of the azimuthal component (By) of the Interplanetary Magnetic Field (IMF) on Magnetosphere-Ionosphere coupling

The solar wind’s IMF By component is believed to be the cause of a number of asymmetric features in both the magnetosphere and ionosphere. We investigate it's role in the generation of Birkeland currents, comparing observations from AMPERE and MHD simulations. When the IMF reconnects with the terrestrial magnetic field with a non-vanishing By flux transport is asymmetrically distributed between the two hemispheres. The magnetosphere then imposes asymmetric forces on the ionosphere, and the effects on ionospheric flow is 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 non-uniform induced By in the closed magnetosphere. By including the dynamics of the system we introduce a mechanism that predicts asymmetric Birkeland currents at conjugate footpoints. We argue that the induced By produces asymmetrical Birkeland currents as a consequence of asymmetric stress balance between the hemispheres. Associated with these currents we expect fast localized ionospheric azimuthal flows present in one hemisphere, but not necessarily in the other.