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Ann. Geophys., 26, 281-293, 2008
www.ann-geophys.net/26/281/2008/
© European Geosciences Union 2008
Comparison of simulated and observed large-scale, field-aligned current structures
P. Nenovski
Geophysical Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Abstract. Recently, a model of large-scale, field-aligned current (FAC) structures, based
on zero-frequency MHD surface wave (SW) modes that can emerge from the solar
wind-Earth's magnetosphere interaction, has been proposed. The FAC polarity
and intensity distribution are quantified as a function of the solar wind
parameters and the interplanetary magnetic field (IMF) magnitude that enter
as input parameters. Besides, there are input parameters intrinsic to the
Earth's magnetosphere – the size of the polar cap and the boundary regions
and their plasma density variations. Influence of the IMF By component
on the FAC structure is examined here. Depending on the IMF By
magnitude, the predicted six-cell FAC structure tends to evolve in a spiral-like fashion.
This large-scale FAC model is compared with experimental evidences and
empirical FAC models based on DE-2 satellite data and high-precision Oersted
and Magsat satellite magnetometer data. Among the various achievements of these
long-term satellite measurements, an observation/discovery of a ground-based
state of FACs which includes a pair of large-scale FACs in the polar cap under
both positive and negative IMF Bz has been pointed out. The FAC pattern
is qualitatively and quantitatively consistent with experimental data for
both polar cap FAC and Region 1 and Region 2 FAC systems.
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