Upper Atmospheric Modifications Caused Energy Transfer via Field-aligned Currents: Opportunities Provided by the Swarm
Lühr, Hermann; Park, Jaeheung; Ritter, Patricia
Deutsches GeoForschungsZentrum GFZ, GERMANY
One of the important mechanisms for lossless energy transfer are electric currents flowing along geomagnetic field lines. These field-aligned currents (FACs) play a prime role in routing energy from the solar wind into the upper atmosphere at auroral latitudes. Since their first experimental verification during the late 1970’s FACs have been the subject of many studies based on satellite observations. Unfortunately, current density estimates based on single satellite measurements depend on a number of simplifying assumptions. Therefore the reliability of so far presented FAC distributions is not fully known. With the advent of ESA’s constellation mission Swarm it is for the first time possible to make unique FAC measurements in the ionosphere. We are going to present the applied approach. A direct consequence of intense FACs is the local heating of the upper atmosphere. Particularly clear effects can be observed in the auroral region around the noon sector. Significant local air density enhancements up to a factor of 2 have been recorded in this cusp region. This air density anomaly has a non-negligible effect on the orbit dynamics of spacecraft and debris passing this region. We will present the mechanisms responsible for the air density anomaly in the auroral cusp region.