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| Titel |
Energy Transfer and Flow in the Solar Wind-Magnetosphere-Ionosphere System: A New Coupling Function |
| VerfasserIn |
Paul Tenfjord, Nikolai Østgaard |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074070
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| Zusammenfassung |
| A fundamental question in space physics is to understand how the flow of energy is
transported and distributed in the solar wind-magnetosphere-ionosphere system. There is no
direct method of measuring the energy transfer from the solar wind to the magnetosphere, but
it is well accepted that the rate of transfer is strongly related to the magnitude of the
southward component (Bz < 0) of the Interplanetary Magnetic Field (IMF). During such
conditions, energy is transferred to the magnetosphere as a consequence of a large-scale
reconnection process on the dayside. Eventually, reconnection in the neutral sheet of the
magnetotail deposits the accumulated energy to the inner magnetosphere and ionosphere.
Joule heating, particle precipitation and ring current injection are the three major
energy sinks in the magnetosphere-ionosphere system. The deposited energy into
these sinks can be estimated using ground-based magnetometer data. In this paper
we determine the functional dependence on solar wind parameters of the rate of
energy transfer from the solar wind into the magnetosphere using a correlation
analysis between the general formula by Vasyliunas et al. [1982] and estimated
energy sinks. Using a superposed epoch analysis for 45 geomagnetic storms, we
have obtained a new energy coupling function describing direct energy transfer. We
find that the effective area of interaction is dynamic, and depends to the first order
on the magnitude of Bz. We also find that for longer time periods this area must
be increased compared to the area used for geomagnetic storms. We quantify the
relative importance of the different energy dissipation processes during substorms,
geomagnetic storms and long time series, and present the coupling efficiency of the
solar wind. Our energy coupling functions is compared with the ε parameter by
Akasofu and Perreault [1978] and is found to perform better for almost every event. |
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