Influence of plasma beta on the generation of lower hybrid and whistler waves by an ion velocity ring distribution
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
We present results of three-dimensional electromagnetic particle-in-cell simulations of the lower hybrid ion ring instability, similar to our earlier results [D. Winske and W. Daughton, Phys. Plasma 19, 072109 (2012)], but at higher electron beta (β{sub e} = ratio of electron thermal pressure to magnetic pressure = 0.06, rather than at 0.006) with T{sub i} = T{sub e}. At higher electron beta, the level of lower hybrid waves at saturation normalized to the ion thermal energy (β{sub i} = 0.06 also) is only slightly smaller, but the corresponding magnetic fluctuations are about an order of magnitude larger, consistent with linear theory. After saturation, the waves evolve into whistler waves, through a number of possible mechanisms, with an average growth rate considerably smaller than the linear growth rate of the lower hybrid waves, to a peak fluctuation level that is about 20% above the lower hybrid wave saturation level. The ratio of the peak magnetic fluctuations associated with the whistler waves relative to those of the saturated lower hybrid waves, the ratio of the nonlinear growth rate of whistlers relative to the linear growth rate of lower hybrid waves, the amount of energy extracted from the ring, and the amount of heating of the background ions and electrons are comparable to those in the lower electron beta 3D simulation. This suggests that even at higher electron beta, the linear and nonlinear physics of the lower hybrid ion ring instability is dominated by electrostatic, wave-particle rather than wave-wave interactions.
- OSTI ID:
- 22408055
- Journal Information:
- Physics of Plasmas, Vol. 22, Issue 2; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Understanding and Harnessing the Dual Electrostatic/Electromagnetic Character of Plasma Turbulence in the Near‐Earth Space Environment
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journal | December 2019 |
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