Altitude distribution of the auroral acceleration potential determined from Cluster satellite data at different heights
Publication date: 01 Feb 2011
Authors: Marklund, G., et al.
Journal: Physical Review Letters
Copyright: American Physical SocietyAurora, commonly seen in the polar sky, is a ubiquitous phenomenon occurring on Earth and other solar system planets. The colorful emissions are caused by high-energy beams of electrons hitting the upper atmosphere, after being accelerated by quasi-static electric fields at altitudes around one Earth radius, or by wave electric fields. Although the aurora was studied by many past satellite missions, Cluster is first to explore the acceleration region with multi-probes, enabling open issues on its nature to be resolved. Here, Cluster data from the upper and lower parts of this region are used to determine the altitude distribution of the acceleration potential above the Aurora Borealis, and to address its stability in space and time. The derived acceleration potential consists of two broad Ushaped potentials in the upper parts of the acceleration region, and a narrower S-shaped potential structure located below, and is stable on a five minute time scale. The results demonstrate that the spatial scale of the electric field is much smaller than the current width in the lower parts, but almost equal in the upper parts of the acceleration region Revealing of these features was possible only by combining data from the two spacecraft.