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Journal Article

How the IMF By induces a local By component during northward IMF Bz and characteristic timescales


Haaland,  Stein
Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society;

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Tenfjord, P., Østgaard, N., Haaland, S., Snekvik, K., Laundal, K. M., Reistad, J. P., et al. (2018). How the IMF By induces a local By component during northward IMF Bz and characteristic timescales. Journal of Geophysical Research: Space Physics, 123(5), 3333-3348. doi:10.1002/2018JA025186.

Cite as: https://hdl.handle.net/21.11116/0000-0001-1DC8-E
We use the Lyon‐Fedder‐Mobarry (LFM) 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 IMF Bz>0.

We describe the evolution of how a magnetospheric By 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 By component. We show the radial dependence of the induced By, and compare the results to the induced By during southward IMF conditions.

We also show the response and reconfiguration time of the inner magnetosphere to IMF By reversals during northward IMF Bz. A superposed epoch analysis of magnetic field measurements from seven Geostationary Operational Environmental Satellite (GOES) spacecraft at different local times both for negative‐to‐positive, and positive‐to‐negative IMF By reversals is presented. We find that the induced By responds within 16 minutes of the arrival of IMF By at the bow‐shock, and it completely reconfigures within 47 minutes.