EVOLUTION OF ELECTRIC FIELDS
IN THE AURORAL RETURN CURRENT REGION
OBSERVED BY CLUSTER NEAR PERIGEE
G. T. Marklund, N.Ivchenko, T. Karlsson, P.-A. Lindqvist
Alfven Laboratory, Royal Institute of Technology,
SE 10044 Stockholm, Sweden
S. Buchert, Andris Vaivads, M. Andre,
Swedish Institute of Space Physics, Angstrmlaboratoriet,
Box 534, 75121 Uppsala, Sweden
A. Fazakerley, C. Owen, M. Taylor, P. Carter
University College, London, Mullard Space Science Laboratory, Holmbury St Mary,
Dorking Surrey RH5 6 NT, United Kingdom
M. Dunlop, A. Balogh
Imperial College, Blackett Laboratory, Space and Atmospheric Physics Group,
London SW7 2 BW, United Kingdom
Press Conference held at the AGU Fall Meeting,
San Francisco, 2001-12-11
EVOLUTION OF ELECTRIC FIELDS ACCELERATING
ELECTRONS AWAY FROM THE AURORAL IONOSPHERE
What is new?
Auroral crossings by Cluster at high altitude (4.4 RE) -- when the
s/c were aligned like pearls-on-a-string -- have allowed the first
detailed studies of the temporal evolution of electric potential
structures that accelerate electrons away from the auroral
ionosphere.
Why Cluster?
To reveal the nature of such acceleration structures it is necessary
to understand their temporal behavior, which cannot be resolved
from single satellite measurements (e.g. Freja, Polar, FAST).
Time-scale of evolution
The time-scale of evolution (a few 100 seconds) is similar to
formation time of ionospheric density holes caused by the upward
escape of electrons indicating a close relationship
Auroral Return Current - Density Holes - Black Aurora
The upward escaping electrons: 1) carry the return current; 2)
produce density holes and sometimes 3) the optical phenomenon
Black Aurora, like a photographic negative of the aurora
Possible impact on the discrete aurora
A common current system links the downward return current with
the upward current of the aurora. The evolution of the ionospheric
density hole and acceleration structure above i