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Physics Of Plasmas

Publication date: 2017-03-01
Volume: 24
Publisher: AIP Publishing

Author:

Lazar, M

Keywords:

Science & Technology, Physical Sciences, Physics, Fluids & Plasmas, Physics, ELECTRON DISTRIBUTIONS, TEMPERATURE, INSTABILITY, ANISOTROPY, 0201 Astronomical and Space Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 0203 Classical Physics, Fluids & Plasmas, 5106 Nuclear and plasma physics, 5109 Space sciences

Abstract:

© 2017 Author(s). This Brief Communication presents a straightforward analytical method for estimating the effects of suprathermal particle populations present in space plasmas, based on a refined Kappa modelling of the velocity distributions which enables comparison with the thermal (core) component. If the observed distribution with suprathermal tails can be reproduced by a Kappa power-law, the core is extracted as a particular Maxwellian limit which needs to be cooler and contain a less number of particles. This approach enables study of the kinetic instabilities driven by anisotropic bi-Kappa distributions, among other applications. Thus, the electromagnetic electron cyclotron instability is found to be stimulated by the suprathermal electrons, confirming the existence of an additional free energy in these populations. Limiting to a standard Maxwellian modelling, as was and still is customary for the analysis of distributions observed in the solar wind, may therefore lead to misleading interpretations of these instabilities and other kinetic effects involving suprathermal populations.