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Ann. Geophys., 21, 881-891, 2003
www.ann-geophys.net/21/881/2003/
© European Geosciences Union 2003
Generation of Bernstein waves by ion shell distributions in the auroral region
P. Janhunen1, A. Olsson2, A. Vaivads2, and W. K. Peterson3
1Finnish Meteorological Institute, Geophysical Research, Helsinki, Finland
2Swedish Institute of Space Physics, Uppsala Division, Uppsala, Sweden
3LASP, University of Colorado, Boulder, Colorado, USA
Abstract. Hot ion shell
distributions could possibly contain enough free energy for waves that could
power electron energisation above auroral inverted-V regions. Using both linear
theory (WHAMP) and two-dimensional electrostatic simulations, we show that ion
shell distributions can cause unstable ion Bernstein mode emissions with high
temporal growth rates, as well as perpendicular and parallel e-folding
distances, that are in accordance with the tranverse dimensions of auroral arcs
and the parallel size of the energisation region, respectively. The phase
velocities of the waves are in the proper range to give parallel energisation
to electrons with a Landau resonance. The simulation shows that about 90% of
the energy goes into electrons and 10% goes into cold ion perpendicular
heating. An electron heating rate of ~ 80 eV/s is obtained.
Key words. Ionosphere (auroral
phenomena) – Space plasma physics (numerical simulation studies;
wave-particle interactions)
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