Variations of the magnetic declination at mid-latitude European stations during the Carrington-like event on 29 October 2003

Abstract. Based on the declination observed at mid-latitude European stations, we studied the current system that is a candidate for the cause of the sharp drop in horizontal intensity (H) of the geomagnetic field that occurred in that part of the globe on 29 October 2003. The newest knowledge says that the current system consisted of a pair of field-aligned currents (FACs) forming a dayside current wedge: in the early afternoon sector, it was a stationary upward FAC, and in the dawn sector, it was a westward-moving downward FAC. We found the velocity of −1.08 °/min ± 0.38 °/min for the wedge centre, roughly half the velocity of the westward-moving downward FAC. Our results contribute to arguments that the dayside current wedge was the probable cause of the H-drop on 29 October 2003.