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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 25, issue 1
Ann. Geophys., 25, 317–330, 2007
https://doi.org/10.5194/angeo-25-317-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 25, 317–330, 2007
https://doi.org/10.5194/angeo-25-317-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.

  01 Feb 2007

01 Feb 2007

Sheared magnetospheric plasma flows and discrete auroral arcs: a quasi-static coupling model

M. M. Echim*,1, M. Roth1, and J. De Keyser1 M. M. Echim et al.
  • 1BIRA-IASB, Avenue Circulaire 3, 1180 Bruxelles, Belgium
  • *also at: the Institute for Space Sciences, Atomiştilor 409, 077125 Măgurele, Romania

Abstract. We consider sheared flows in magnetospheric boundary layers of tangential discontinuity type, forming a structure that is embedded in a large-scale convergent perpendicular electric field. We construct a kinetic model that couples the magnetospheric structure with the topside ionosphere. The contribution of magnetospheric electrons and ionospheric electrons and ions is taken into account into the current-voltage relationship derived for an electric potential monotonically decreasing with the altitude. The solution of the current continuity equation gives the distribution of the ionospheric potential consistent with the given magnetospheric electric potential. The model shows that a sheared magnetospheric flow generates current sheets corresponding to upward field-aligned currents, field-aligned potential drops and narrow bands of precipitating energy, as in discrete auroral arcs. Higher velocity magnetospheric sheared flows have the tendency to produce brighter and slightly broader arcs. An increase in arc luminosity is also associated with enhancements of magnetospheric plasma density, in which case the structures are narrower. Finally, the model predicts that an increase of the electron temperature of the magnetospheric flowing plasma corresponds to slightly wider arcs but does not modify their luminosity.

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