The Ørsted Satellite Project

A Danish Microsatellite With a High Scientific Profile

Papers and reports


FIRST DETECTION OF GLOBAL DAWN-DUSK IONOSPHERIC CURRENT INTENSITIES USING AMPÈRE'S INTEGRAL LAW ON ØRSTED SATELLITE ORBITS

 

Stauning, P. (1), and F. Primdahl (2,3)

  1. Solar-Terrestrial Physics Division, Danish Meteorological Institute, Lyngbyvej 100, DK-2100 Copenhagen, Denmark. Fax.: +45 39 15 74 60 E-mail: pst@dmi.dk.

  2. Technical University of Denmark, Department of Automation, Building 327, DK-2800 Lyngby, Denmark. E-mail: fp@iau.dtu.dk

  3. Danish Space Research Institute, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark.

Abstract. The magnetic measurements by the Ørsted satellite in noon-midnight orbits have enabled the derivation of the global dawn-dusk oriented ionospheric currents from an Ampère’s law closed loop line integral of the geomagnetic vector field along the satellite track. The dawn-to-dusk ionospheric current intensities are found to be proportional to the geo-effective solar wind electric fields. The total dawn-to-dusk current through the satellite orbit is around 1 million ampère for a typical solar wind electric field of 2 mV/m. Dividing the Ampère integral into semi-orbit parts has enabled us to show that the hemispherical total current intensities depend on the respective polar cap conductivities, which relate to the daily and seasonally varying solar illumination. The more illuminated hemisphere conveys up to three times more current from dawn to dusk than does the less illuminated.