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| Titel |
On estimating the properties of the auroral magnetospheric generator from ionospheric observations of discrete auroral arcs and a magnetosphere-ionosphere coupling. |
| VerfasserIn |
H. Lamy, M. Echim, C. Simon Wedlund |
| 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 |
250065093
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| Zusammenfassung |
| We propose a method to estimate the properties of the auroral generator, like electron density
(ne) and temperature (Te), from ionospheric observations of the energy flux of precipitating
electrons, É, measured across an auroral arc. For this purpose, we use a quasi-static
magnetosphere-ionosphere (M-I) coupling model based on the current continuity in the
ionosphere (Echim et al, 2007) and a kinetic description of the magnetospheric generator
derived from the models of tangential discontinuities (Roth et al 1993). The model is run
iteratively for typical values of magnetospheric ne and Tethat are adjusted until Ég the
precipitating energy flux provided by the model, fits the ionospheric observations. The latter
can be obtained either from in-situ spacecraft measurements or from optical ground-based
observations.
First, we test the method by using the precipitating energy flux observed by DMSP on
April 28, 2001, above a discrete auroral arc. For this particular date we have been able to
compare the generator properties determined with our method with actual magnetospheric
in-situ data provided by Cluster. The results compare very well and hence validate the
method.
Next, we use the energy flux of precipitating electrons obtained from optical images of
discrete auroral arcs obtained simultaneously with the CCD cameras of the ALIS (Auroral
Large Imaging System) network located in Scandinavia. Indeed, with tomography-like
techniques, the three-dimensional (3D) volume emission rates at 4278 Å can be retrieved and
used to derive the energy spectra of precipitating magnetospheric electrons in 2D, along and
across the arc, with a spatial resolution of approximately 3 km. These spectra directly provide
E0, the characteristic energy and É, the total flux energy of precipitating electrons. The
generator properties are derived from this new set of auroral observations using the iterative
technique validated with data from the DMSP-Cluster conjunction. We thus discuss
a new method to explore the properties of the quasi-stationary magnetospheric
generator of auroral arcs from ionospheric observations of the precipitating energy flux |
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