How the IMF $B_y$ Induces a Local $B_y$ Component During Northward IMF $B_z$ and Characteristic Timescales

Abstract

We use the Lyon-Fedder-Mobarry global magnetohydrodynamics model to study the effects of the interplanetary magnetic field (IMF) $B_y$ component on the coupling between the solar wind and magnetosphere-ionosphere system when IMF $B_z$ $>$0. We describe the evolution of how a magnetospheric $B_y$ component is induced on closed field lines during these conditions. Starting from dayside lobe reconnection, the magnetic tension on newly reconnected field lines redistribute the open flux asymmetrically between the two hemispheres. This results in asymmetric magnetic energy density in the lobes. Shear flows are induced to restore equilibrium, and these flows are what effectively induces a local $B_y$ component. We show the radial dependence of the induced $B_y$ and compare the results to the induced $B_y$ during southward IMF conditions. We also show the response and reconfiguration time of the inner magnetosphere to IMF $B_y$ reversals during northward IMF $B_z$. A superposed epoch analysis of magnetic field measurements from seven Geostationary Operational Environmental Satellite spacecraft at different local times both for negative-to-positive and positive-to-negative IMF $B_y$ reversals is presented. We find that the induced $B_y$ responds within 16 min of the arrival of IMF $B_y$ at the bow shock, and it completely reconfigures within 47 min.

References in corpus (4)

• 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
• Comparative Analysis of Dayside Reconnection Models in Global Magnetosphere Simulations
• The interaction between transpolar arcs and cusp spots
• Dynamic effects of restoring footpoint symmetry on closed magnetic field lines

Cited by in corpus (2)

• Observations of Asymmetries in Ionospheric Return Flow During Different Levels of Geomagnetic Activity
• Observations of Asymmetric Lobe Convection for Weak and Strong Tail Activity