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| Titel |
Energy exchange rates between the ionosphere-thermosphere system and the magnetosphere at high latitudes |
| VerfasserIn |
A. Aikio, L. Cai, T. Nygrén, R. Kuula |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066506
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| Zusammenfassung |
| The magnetosphere and the ionosphere-thermosphere system exchange energy in the form of
electromagnetic energy flux, accompanied by electric fields and field-aligned currents, as well
as in the form of precipitating particle fluxes. In this study, we examine the first form of
energy exchange by using a one-month database obtained by the EISCAT incoherent scatter
radar measurements in Tromso. The electromagnetic energy exchange rate can be further
divided into ion-neutral frictional heating rate (sometimes called Joule heating) and work
done on neutrals. The ion-neutral frictional heating rate depends on Pedersen conductivity
and on ionospheric electric fields, measured in the frame of reference moving with the
neutrals. The role of neutral winds has been an open question, since it is difficult
to measure them. The CP2 scan mode of the EISCAT radar makes it possible to
deduce neutral winds in the E region and hence to estimate the role of neutral air
motion (e.g. tidal winds and atmospheric gravity waves) in the energy exchange
rates.
In this talk, we will present the magnetic local time (MLT) dependence of height-integrated
quantities: electromagnetic energy exchange rates (QEM), ion-neutral frictional heating rate
(QJ) and work done on neutrals (Qm) for different magnetic activity levels categorized by
the Kp index. We will show that the role of winds is different in different MLT sectors (e.g.
dusk vs. dawn) and at different activity levels. We will also show that on rare occasions the
ionosphere can act as a dynamo generating electromagnetic energy that may propagate to the
magnetosphere. |
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