Wu, H;
Verscharen, D;
Wicks, RT;
Chen, CHK;
He, J;
Nicolaou, G;
(2019)
The Fluid-like and Kinetic Behavior of Kinetic Alfven Turbulence in Space Plasma.
Astrophysical Journal
, 870
(2)
, Article 106. 10.3847/1538-4357/aaef77.
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Abstract
Kinetic Alfvén waves (KAWs) are the short-wavelength extension of the magnetohydrodynamics Alfvén-wave branch in the case of highly oblique propagation with respect to the background magnetic field. Observations of space plasma show that small-scale turbulence is mainly KAW-like. We apply two theoretical approaches, a collisional two-fluid theory and a collisionless linear kinetic theory, to obtain predictions for the KAW polarizations depending on βp (the ratio of the proton thermal pressure to the magnetic pressure) at the ion gyroscale in terms of fluctuations in density, bulk velocity, and pressure. We perform a wavelet analysis of Magnetospheric Multiscale magnetosheath measurements and compare the observations with both theories. We find that the two-fluid theory predicts the observations better than the kinetic theory, suggesting that the small-scale KAW-like fluctuations exhibit a fluid-like behavior in the magnetosheath although the plasma is weakly collisional. We also present predictions for the KAW polarizations in the inner heliosphere that are testable with Parker Solar Probe and Solar Orbiter.
| Type: | Article |
|---|---|
| Title: | The Fluid-like and Kinetic Behavior of Kinetic Alfven Turbulence in Space Plasma |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/aaef77 |
| Publisher version: | https://doi.org/10.3847/1538-4357/aaef77 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 3.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/ |
| Keywords: | magnetohydrodynamics (MHD) – plasmas – solar–terrestrial relations – turbulence – waves |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics > Advanced Instrumentation Systems |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10060990 |
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