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Ann. Geophys., 23, 2117-2128, 2005
www.ann-geophys.net/23/2117/2005/
© European Geosciences Union 2005
The relationship between auroral hiss at high altitudes over the polar caps and the substorm dynamics of aurora
E. E. Titova1, A. G. Yahnin1, O. Santolík2, D. A. Gurnett3, F. Jirícek4, J.-L. Rauch5, F. Lefeuvre5, L. A. Frank3, J. B. Sigwarth3, and M. M. Mogilevsky6
1Polar Geophysical Institute, Apatity, Russia
2Faculty of Mathematics and Physics, Charles University and Institute of Atmospheric Physics, Prague, Czech Republic
3Department of Physics and Astronomy, University of Iowa, Iowa City, USA
4Institute of Atmospheric Physics, Prague, Czech Republic
5LPCE/CNRS, Orleans, France
6Institute of Space Research, Moscow, Russia
Abstract. Strong variations of intensity
and cutoff frequency of the auroral hiss were observed by INTERBALL-2 and
POLAR satellites at high altitudes, poleward from the auroral oval. The hiss
intensifications are correlated with the auroral activations during
substorms and/or pseudo-breakups. The low cutoff frequency of auroral hiss
increases with the distance between the aurora and the satellite footprint.
Multicomponent wave measurements of the hiss emissions on board the POLAR
spacecraft show that the horizontal component of the Poynting flux of
auroral hiss changes its direction in good accordance with longitudinal
displacements of the bright auroras. The vertical component of the Poynting
flux is directed upward from the aurora region, indicating that hiss could be
generated by upgoing electron beams. This relationship between hiss and the
aurora dynamics means that the upgoing electron beams are closely related to
downgoing electron beams which produce the aurora. During the auroral
activations the upgoing and downgoing beams move and change their
intensities simultaneously.
Keywords. Magnetospheric physics (Auroral phenomena;
Plasma waves and instabilities; Storms and substorms)
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