|
|
 |
|
|
Ann. Geophys., 22, 1719-1728, 2004
www.ann-geophys.net/22/1719/2004/
© European Geosciences Union 2004
A linear auroral current-voltage relation in fluid theory
J. Vedin and K. Rönnmark
Department of Physics, Umeå University, SE-901 87 Umeå, Sweden
Abstract. Progress in our understanding of auroral currents and auroral
electron acceleration has for decades been hampered by an apparent
incompatibility between kinetic and fluid models of the physics
involved. A well established kinetic model predicts that steady
upward field-aligned currents should be linearly related to the
potential drop along the field line, but collisionless fluid models
that reproduce this linear current-voltage relation have not been
found. Using temperatures calculated from the kinetic model in the
presence of an upward auroral current, we construct here
approximants for the parallel and perpendicular temperatures.
Although our model is rather simplified, we find that the fluid
equations predict a realistic large-scale parallel electric field
and a linear current-voltage relation when these approximants are
employed as nonlocal equations of state. This suggests that the
concepts we introduce can be applied to the development of accurate
equations of state for fluid simulations of auroral flux tubes.
Key words. Magnetospheric physics (auroral phenomena;
magnetosphere-ionosphere interactions) – Space plasma
physics (kinetic and MHD theory)
Full Article in PDF (302 KB) |
|
|
