Articles | Volume 34, issue 10
Ann. Geophys., 34, 901–915, 2016
Ann. Geophys., 34, 901–915, 2016

Regular paper 24 Oct 2016

Regular paper | 24 Oct 2016

Filamentary field-aligned currents at the polar cap region during northward interplanetary magnetic field derived with the Swarm constellation

Hermann Lühr1, Tao Huang1,2, Simon Wing3, Guram Kervalishvili1, Jan Rauberg1, and Haje Korth3 Hermann Lühr et al.
  • 1GFZ, German Research Centre for Geosciences, Section 2.3 “Earth's Magnetic Field”, 14473 Potsdam, Germany
  • 2Department of Space Physics, College of Electronic Information, Wuhan University, 430072 Wuhan, China
  • 3The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, USA

Abstract. ESA's Swarm constellation mission makes it possible for the first time to determine field-aligned currents (FACs) in the ionosphere uniquely. In particular at high latitudes, the dual-satellite approach can reliably detect some FAC structures which are missed by the traditional single-satellite technique. These FAC events occur preferentially poleward of the auroral oval and during times of northward interplanetary magnetic field (IMF) orientation. Most events appear on the nightside. They are not related to the typical FAC structures poleward of the cusp, commonly termed NBZ. Simultaneously observed precipitating particle spectrograms and auroral images from Defense Meteorological Satellite Program (DMSP) satellites are consistent with the detected FACs and indicate that they occur on closed field lines mostly adjacent to the auroral oval. We suggest that the FACs are associated with Sun-aligned filamentary auroral arcs. Here we introduce in an initial study features of the high-latitude FAC structures which have been observed during the early phase of the Swarm mission. A more systematic survey over longer times is required to fully characterize the so far undetected field aligned currents.

Short summary
ESA's constellation mission Swarm makes it possible for the first time to determine field-aligned currents (FACs) reliably in the ionosphere. FACs are able to transport energy from the solar wind to the Earth and heat the upper atmosphere. Here we investigate FAC structures that have been missed by previous satellite missions. Most of them are found poleward of the northern light zone. The energy sources seem to be located on the nightside of Earth about 100 000 km away.