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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 1
Ann. Geophys., 22, 125–140, 2004
https://doi.org/10.5194/angeo-22-125-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 125–140, 2004
https://doi.org/10.5194/angeo-22-125-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  01 Jan 2004

01 Jan 2004

Quantitative modelling of the closure of meso-scale parallel currents in the nightside ionosphere

A. Marchaudon1, J.-C. Cerisier1, O. Amm2, M. Lester3, C. W. Carlson4, and G. K. Parks4 A. Marchaudon et al.
  • 1Centre d’Etude des Environnements Terrestre et Planétaires, 4 avenue de Neptune, 94107 Saint-Maur-des-Fossés Cedex, France
  • 2Geophysical Research Division, Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland
  • 3Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
  • 4Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450, USA

Abstract. On 12 January 2000, during a northward IMF period, two successive conjunctions occur between the CUTLASS SuperDARN radar pair and the two satellites Ørsted and FAST. This situation is used to describe and model the electrodynamic of a nightside meso-scale arc associated with a convection shear. Three field-aligned current sheets, one upward and two downward on both sides, are observed.

Based on the measurements of the parallel currents and either the conductance or the electric field profile, a model of the ionospheric current closure is developed along each satellite orbit. This model is one-dimensional, in a first attempt and a two-dimensional model is tested for the Ørsted case. These models allow one to quantify the balance between electric field gradients and ionospheric conductance gradients in the closure of the field-aligned currents.

These radar and satellite data are also combined with images from Polar-UVI, allowing for a description of the time evolution of the arc between the two satellite passes. The arc is very dynamic, in spite of quiet solar wind conditions. Periodic enhancements of the convection and of electron precipitation associated with the arc are observed, probably associated with quasi-periodic injections of particles due to reconnection in the magnetotail. Also, a northward shift and a reorganisation of the precipitation pattern are observed, together with a southward shift of the convection shear.

Key words. Ionosphere (auroral ionosphere; electric fields and currents; particle precipitation) – Magnetospheric physics (magnetosphere-ionosphere interactions)

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