Simulations of Plasmapause Deformations During Magnetic Substorms and Other
Variations in the Level of Geomagnetic Activity

V. Pierrard (Belgian Institute for Space Aeronomy, B-1180 Brussels, Belgium)
and J.F. Lemaire

The theory for the plasmapause formation based on interchange instability and
a Kp-dependent magnetospheric electric field model, enables to determine the
position of the plasmapause as a function of Kp and local time. We show
dynamical simulations of plasmapause for typical changes in the level of
geomagnetic activity, and illustrate how this physical mechanism is able to
account for the formation of shoulders like those observed by EUV on IMAGE. A
wide variety of other structures observed by IMAGE like tails (also called
plumes), and notches are also obtained within the framework of this theory
for the formation of a "knee" in the high altitude cross-L distribution of
the cold plasma density distribution. The positions of the plasmapause in the
midnight LT sector predicted for different values of Kp by this plasmapause
formation mechanism are compared to various empirical relationships deduced
from whistler and in situ satellite observations.  

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Presentation at the Yosemite Conference of Inner Magnetospheric Interactions,
3 - 6 February 2004, Yosemite, California, USA