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Volume 31, issue 3
Ann. Geophys., 31, 451–457, 2013
https://doi.org/10.5194/angeo-31-451-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 31, 451–457, 2013
https://doi.org/10.5194/angeo-31-451-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

ANGEO Communicates 07 Mar 2013

ANGEO Communicates | 07 Mar 2013

Ion temperature anisotropy effects on threshold conditions of a shear-modified current driven electrostatic ion-acoustic instability in the topside auroral ionosphere

P. J. G. Perron1, J.-M. A. Noël1, K. Kabin1, and J.-P. St-Maurice2 P. J. G. Perron et al.
  • 1Department of Physics, Royal Military College of Canada, Kingston, Ontario, Canada
  • 2Institute of Space and Atmospheric Studies and Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Abstract. Temperature anisotropies may be encountered in space plasmas when there is a preferred direction, for instance, a strong magnetic or electric field. In this paper, we study how ion temperature anisotropy can affect the threshold conditions of a shear-modified current driven electrostatic ion-acoustic (CDEIA) instability. In particular, this communication focuses on instabilities in the context of topside auroral F-region situations and in the limit where finite Larmor radius corrections are small. We derived a new fluid-like expression for the critical drift which depends explicitly on ion anisotropy. More importantly, for ion to electron temperature ratios typical of F-region, solutions of the kinetic dispersion relation show that ion temperature anisotropy may significantly lower the drift threshold required for instability. In some cases, a perpendicular to parallel ion temperature ratio of 2 and may reduce the relative drift required for the onset of instability by a factor of approximately 30, assuming the ion-acoustic speed of the medium remains constant. Therefore, the ion temperature anisotropy should be considered in future studies of ion-acoustic waves and instabilities in the high-latitude ionospheric F-region.

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