Effect of general loss-cone distribution function on the shear-driven electrostatic ion-cyclotron instability |
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| Institution: | 1. Department of Physics and Astronomy, Uppsala University, Box 516, SE 751 20 Uppsala, Sweden;2. Swedish Institute of Space Physics, Box 537, SE 751 21 Uppsala, Sweden;3. Space and Science Engineering Division, Southwest Research Institute (SWRI), 6220 Culebra Road, San Antonio, TX 78238, USA;1. Arctic and Antarctic Research Institute, 38, Bering Street, St. Petersburg 199397, Russia;2. Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK;3. EISCAT Scientific Association, Kiruna SE-961 28, Sweden;1. Université Versailles St-Quentin, Sorbonne Universités, UPMC Univ. Paris 06, CNRS/INSU, LATMOS-IPSL, 11 Boulevard d’Alembert, 78280 Guyancourt, France;2. Institut Universitaire de France, 103 Bvd. St-Michel, 75005 Paris, France;3. LGPM, Ecole centrale de Paris, Grande voie des Vignes, 92295 Chatenay-Malabry Cedex, France;1. Aix-Marseille Université, CNRS, PIIM, UMR 7345, 13013 Marseille, France;2. Ice Spectroscopy Lab, Science Division, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA |
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| Abstract: | The shear-driven electrostatic ion-cyclotron instability (EICI) is studied using the loss-cone distribution function by particle aspect analysis. The effect of the loss-cone distribution on the dispersion relation and growth rate of weak shear-driven EICI is studied. The whole plasma is considered to consist of resonant and non-resonant particles. The wave is assumed to propagate obliquely to the static magnetic field. It is found that the frequency of the EICI is Doppler shifted due to the transverse inhomogeneous flow in the direction of the magnetic field. It is also found that for anisotropic plasma the critical velocity shear needed to excite EICI depends upon the loss-cone distribution index (J). With the increasing values the loss-cone distribution indices (J), the critical value of normalized velocity shear needed to generate EICI in anisotropic plasma, decreases and is of the order of the weak shear. The loss-cone distribution acts as a source of free energy and generates the weak shear-driven EICI at longer perpendicular perturbations. It also lowers the transverse and parallel energy of the resonant ions. The study may explain the frequently observed EICI in the auroral acceleration region. |
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