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| Titel |
How the IMF By induces a By-component on closed field lines during northward IMF Bz |
| VerfasserIn |
Paul Tenfjord, Nikolai Østgaard, Robert J. Strangeway, Jone Reistad, Karl Magnus Laundal, Stein Haaland, Michael Hesse, Kristian Snekvik, Stephen E. Milan |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148102
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| Publikation (Nr.) |
 EGU/EGU2017-12331.pdf |
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| Zusammenfassung |
| We describe how the IMF By-component induces a local By-component on closed field lines
during northward IMF Bz. The mechanism is the result of high-latitude reconnection on the
dayside when IMF By is non-zero. We describe the dynamical process, in which tension on
newly reconnected field lines redistribute the open flux asymmetrically between the two
hemispheres, which leads to asymmetric energy flow into the lobes. The resulting shear flows
change the magnetic field, thereby inducing a By-component on closed field lines. We use a
global magnetohydrodynamics model to illustrate the mechanism. The magnetosphere
imposes asymmetric forces on the ionosphere, and the effects on the ionospheric flows
are characterized by a departure from a symmetric two-cell configuration to the
growth of one of the lobe cells, while the other will contract. We also present the
associated timescales of the local By-component to a change in the IMF By, by
both theoretical arguments and by a superposed epoch analysis between magnetic
field measurements from GOES and a list of IMF By reversals. We find that the
magnetosphere responds within 10 minutes and reconfigures within 40 minutes. |
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