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Ann. Geophys., 22, 2485-2495, 2004
www.ann-geophys.net/22/2485/2004/
© European Geosciences Union 2004
Intense high-altitude auroral electric fields - temporal and spatial characteristics
T. Johansson1, S. Figueiredo1, T. Karlsson1, G. Marklund1, A. Fazakerley2, S. Buchert3, P.-A. Lindqvist1, and H. Nilsson4
1Division of Plasma Physics, Alfvén Laboratory, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
2Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
3Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
4Swedish Institute of Space Physics, Box 812, SE-981 28 Kiruna, Sweden
Abstract. Cluster electric field, magnetic field, and energetic electron
data are analyzed for two events of intense auroral electric
field variations, both encountered in the Plasma Sheet Boundary
Layer (PSBL), in the evening local time sector, and at
approximately 5RE geocentric distance. The most intense
electric fields (peaking at 450 and 1600mV/m, respectively) were
found to be quasi-static, unipolar, relatively stable on the time
scale of at least half a minute, and associated with moving
downward FAC sheets (peaking at ~10μA/m2), downward
Poynting flux (peaking at ~35mW/m2), and upward
electron beams with characteristic energies consistent with the
perpendicular potentials (all values being mapped to 1RE geocentric distance). For these two events in the return current
region, quasi-static electric field structures and associated
FACs were found to dominate the upward acceleration of electrons,
as well as the energy transport between the ionosphere and the
magnetosphere, although Alfvén waves clearly also contributed
to these processes.
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