Dependence of kinetic plasma waves on ion-to-electron mass ratio and light-to-Alfvén speed ratio
AffiliationUniv Arizona, Lunar & Planetary Lab
Univ Arizona, Dept Planetary Sci
MetadataShow full item record
PublisherOXFORD UNIV PRESS
CitationVerscharen, D., Parashar, T. N., Gary, S. P., & Klein, K. G. (2020). Dependence of kinetic plasma waves on ion-to-electron mass ratio and light-to-Alfvén speed ratio. Monthly Notices of the Royal Astronomical Society, 494(2), 2905-2911.
Rights©2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
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AbstractThe magnetization vertical bar Omega(e)vertical bar/omega(e) is an important parameter in plasma astrophysics, where Omega(e) and omega(e) are the electron gyro-frequency and electron plasma frequency, respectively. It depends only on the mass ratio m(i)/m(e) and the light-to-Alfven speed ratio c/v(Ai), where in, (m(e)) is the ion (electron) mass, c is the speed of light, and v(Ai) is the ion Alfven speed. Non-linear numerical plasma models such as particle-in-cell simulations must often assume unrealistic values for mike and for c/v(Ai). Because linear theory yields exact results for parametric scalings of wave properties at small amplitudes, we use linear theory to investigate the dispersion relations of Alfven/ion-cyclotron and fast-magnetosonic/whistler waves as prime examples for collective plasma behaviour depending on m(i)/m(e) and c/v(Ai). We analyse their dependence on m(i)/m(e) and c/v(Ai) in quasi-parallel and quasi-perpendicular directions of propagation with respect to the background magnetic field for a plasma with beta(j) similar to 1, where beta(j) is the ratio of the thermal to magnetic pressure for species j. Although their dispersion relations are largely independent of c/v(Ai) for c/v(Ai) greater than or similar to 10, the mass ratio mime has a strong effect at scales smaller than the ion inertial length. Moreover, we study the impact of relativistic electron effects on the dispersion relations. Based on our results, we recommend aiming for a more realistic value of m(i)/m(e) than for a more realistic value of c/v(Ai) in non-relativistic plasma simulations if such a choice is necessary, although relativistic and sub-Debye-length effects may require an additional adjustment of c/v(Ai).
VersionFinal published version
SponsorsNational Aeronautics and Space Administration