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Ann. Geophys., 21, 2259-2269, 2003
www.ann-geophys.net/21/2259/2003/
© European Geosciences Union 2003
Two-dimensional current-carrying plasma sheet in the near-Earth geomagnetic tail region:
a quasi-stationary evolution
A. V. Manankova
Institute of Physics, St. Petersburg University, St. Petersburg 198504, Russia
Abstract. A problem concerning stationary
configurations of an inhomogeneous, current-carrying, two-dimensional
plasma sheet as the solution of the Grad–Shafranov equation with
boundary conditions given on cross-sheet profiles at the foot of the
sheet and at infinity is considered, with the aim of using its solution
for the description of the interaction of two current systems: the current
system of the geomagnetic field, and the tail currents. The obtained
solution is an exact analytical solution which contains 5 independent
parameters characterizing the intensity of the current sheet. As the
solution is exact, it may be applied to describe the most interesting
transitional magnetospheric region: that of a strong interaction between
the magnetic fields of the geodipole and of the current sheet, i.e. the
region where characteristic scales of the change of all variables along
and across the sheet are of the same order. This makes it possible to
model the structure of the transitional region and its dynamics under
quasi-stationary variation of the input parameters. The obtained solution
describes the principal processes developing at various phases of
magnetospheric disturbances, such as (1) formation of a very intense thin
current sheet localized within the transition region, (2) changing from
the quasi-dipolar magnetic field to the configuration when a
"neck" is formed in this region. An important feature of the
obtained solution is the existence of a critical value of one of the
parameters of the problem, which leads to the change in the geomagnetic
field configuration described above. The solution can be used as an
initial condition in simulating dynamical processes in the magnetotail
current sheet, as well as in testing the current sheet stability. In the
summary a series of limitations in the model problem under consideration
is discussed.
Key words. Magnetospheric physics (magnetotail;
plasma sheet; magnetospheric configuration and dynamics)
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