The Ørsted Satellite Project

Watermann, J. (1), P. Stauning (1), O. Rasmussen (1), V.O. Papitashvili (2), V.A. Popov (3), and J.P. Thayer (4)

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


2. Space Physics Research Laboratory, University of Michigan, Ann Arbor, MI 48109, USA.


3. Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, IZMIRAN, Troitsk, Moscow Region, Russia.


4. SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025, USA.

Abstract. September 1999 was a magnetically active month, with several magnetospheric storms occurring in sequence which affected the high-latitude ionosphere. The DMI Greenland magnetometers recorded variations of the polar electrojet while Ørsted, a Danish Earth orbiting satellite, measured the magnetic effect of field-aligned currents. We discuss a particular dayside event which occurred a few hours after the peak of a moderate storm on Sept. 15, 1999. Ørsted proceeded polebound on a trajectory closely aligned with the Greenland west coast magnetometer chain, and the Sondrestrom Incoherent Scatter Radar was in operation scanning the ionosphere almost parallel to the Ørsted trajectory. Coincident solar wind (SW) and interplanetary magnetic field (IMF) data were obtained from the ACE spacecraft and ballistically propagated to a nominal subsolar bow shock location at 12 Re. A synoptic view of the data suggests that the dayside field-aligned and ionospheric current system responded quickly (within 5-10 min) to variations of the northward component of the IMF (IMF Bz). Specifically, the latitude of the boundary between westward and eastward electrojet followed closely IMF Bz variations.