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Freja Studies of the Current-Voltage Relation in Substorm-Related EventsField-aligned currents and electrostatic potentials play important roles in the coupling between the magnetosphere and the ionosphere. If one assumes that the ionosphere-magnetosphere potential difference is mainly due to the mirror force, one can use the single particle adiabatic kinetic theory to describe the system. From this theory, a linear relationship j(sub II) = KV between field-aligned current density j(sub II) and potential drop V along the same field line can be derived, provided that the potential drop is not too large and not too small. With rare exceptions, observational tests of this relation have mainly concentrated on quiet magnetospheric situations, with acceleration voltages V approx. less than 5 kV. Here we use observations from the Freja satellite of precipitating auroral electrons at 1.700 km altitude to study substorm related events, with acceleration voltages up to 20 keV. The observations are found to be consistent with a linear current-voltage relation even i n these conditions, although with values of the field aligned K lower than previously reported (1-5 x 10(exp 11 S/sq m). This can be explained by lower densities and higher characteristic electron energies in the magnetospheric source region of the precipitating electrons. We analyze the data by three different methods, which are all found to be in general agreement. The results are in agreement with a previous study, where the spectra of precipitating electrons --were indirectly inferred by inversion of data from the EISCAT incoherent scatter radar, thereby validating the use of radar data for studies of auroral electrons. Comparisons with previous studies are made, emphasizing the dependence of the results on the type of auroral structure and magnetospheric conditions.
Document ID
20010033905
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Olsson, A.
(Swedish Inst. of Space Physics Uppsala, Sweden)
Andersson, Laila
(Swedish Inst. of Space Physics Kiruna, Sweden)
Eriksson, A. I.
(Swedish Inst. of Space Physics Uppsala, Sweden)
Clemmons, J.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Erlandsson, R. E.
(Johns Hopkins Univ. Laurel, MD United States)
Reeves, G.
(Los Alamos National Lab. NM United States)
Hughes, T.
(Herzberg Inst. of Astrophysics Ottawa, Ontario Canada)
Murphee, J. S.
(Calgary Univ. Alberta Canada)
Date Acquired
August 20, 2013
Publication Date
November 1, 2000
Publication Information
Publication: Acceleration Processes in Auroral Region
ISSN: 0284-1703
ISBN: 91-7191-914-7
Subject Category
Meteorology And Climatology
Report/Patent Number
Paper-2
Distribution Limits
Public
Copyright
Other

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