title: Altitude distribution of the auroral acceleration potential determined from cluster satellite data at different heights.
abstract: Aurora, commonly seen in the polar sky, is a ubiquitous phenomenon occurring on Earth and other solar system planets. The colorful emissions are caused by electron beams hitting the upper atmosphere, after being accelerated by quasistatic electric fields at 1-2 R(E) altitudes, or by wave electric fields. Although aurora was studied by many past satellite missions, Cluster is the first to explore the auroral acceleration region with multiprobes. Here, Cluster data are used to determine the acceleration potential above the aurora and to address its stability in space and time. The derived potential comprises two upper, broad U-shaped potentials and a narrower S-shaped potential below, and is stable on a 5 min time scale. The scale size of the electric field relative to that of the current is shown to depend strongly on altitude within the acceleration region. To reveal these features was possible only by combining data from the two satellites.
authors.affiliation: Space and Plasma Physics, School of Electrical Engineering, KTH, SE 10044 Stockholm, Sweden.
authors.forename: Göran T
authors.initials: GT
authors.lastname: Marklund
authors.forename: Soheil
authors.initials: S
authors.lastname: Sadeghi
authors.forename: Tomas
authors.initials: T
authors.lastname: Karlsson
authors.forename: Per-Arne
authors.initials: PA
authors.lastname: Lindqvist
authors.forename: Hans
authors.initials: H
authors.lastname: Nilsson
authors.forename: Colin
authors.initials: C
authors.lastname: Forsyth
authors.forename: Andrew
authors.initials: A
authors.lastname: Fazakerley
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Lucek
authors.forename: Jolene
authors.initials: J
authors.lastname: Pickett