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Nonlinear wave damping due to multi-plasmon resonances
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0003-2716-098X
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
2018 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 60, no 2, article id 025009Article in journal (Refereed) Published
Abstract [en]

For short wavelengths, it is well known that the linearized Wigner-Moyal equation predicts wave damping due to wave-particle interaction, where the resonant velocity shifted from the phase velocity by a velocity v(q) = hk/2m. Here h is the reduced Planck constant, k is the wavenumber and m is the electron mass. Going beyond linear theory, we find additional resonances with velocity shifts nv(q), n= 2,3, ..., giving rise to a new wave-damping mechanism that we term multi-plasmon damping, as it can be seen as the simultaneous absorption (or emission) of multiple plasmon quanta. Naturally this wave damping is not present in classical plasmas. For a temperature well below the Fermi temperature, if the linear (n = 1) resonant velocity is outside the Fermi sphere, the number of linearly resonant particles is exponentially small, while the multi-plasmon resonances can be located in the bulk of the distribution. We derive sets of evolution equations for the case of two-plasmon and three-plasmon resonances for Langmuir waves in the simplest case of a fully degenerate plasma. By solving these equations numerically for a range of wave-numbers we find the corresponding damping rates, and we compare them to results from linear theory to estimate the applicability. Finally, we discuss the effects due to a finite temperature.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018. Vol. 60, no 2, article id 025009
Keywords [en]
wave-particle interaction, Wigner equation, Langmuir waves, nonlinear wave damping
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:umu:diva-143622DOI: 10.1088/1361-6587/aa979dISI: 000418145500002OAI: oai:DiVA.org:umu-143622DiVA, id: diva2:1178571
Funder
Swedish Research Council, 2012-3320Available from: 2018-01-30 Created: 2018-01-30 Last updated: 2019-08-21Bibliographically approved
In thesis
1. Quantum Kinetic Theory for Plasmas: spin, exchange, and particle dispersive effects
Open this publication in new window or tab >>Quantum Kinetic Theory for Plasmas: spin, exchange, and particle dispersive effects
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about developing and studying quantum mechanical models of plasmas. Quantum effects can be important at high densities, at low temperatures, and in strong electromagnetic fields, in various laboratory and astrophysical systems. The focus is on the electron spin, the intrinsic magnetic moment; exchange interactions, a purely quantum mechanical effect arising from particles being indistinguishable; and particle dispersive effects, essentially the Heisenberg uncertainty principle. The focus is on using phase-space formulations of quantum mechanics, namely Wigner and -functions. These methods allow carrying over techniques from classical plasma physics and identifying quantum as opposed to classical behavior.

Two new kinetic models including the spin are presented, one fully relativistic and to first order in ħ, and one semi-relativistic but to all orders in ħ. Among other example calculations, for the former, conservation laws for energy, momentum, and angular momentum are derived and related to “hidden momentum” and the Abraham-Minkowski dilemma. Both models are discussed in the context of the existing literature.

A kinetic model of exchange interactions, formally similar to a collision operator, is compared to a widely used fluid description based on density functional theory, for the case of electrostatic waves. The models are found to disagree significantly.

A new, non-linear, wave damping mechanism is shown to arise from particle dispersive effects. It can be interpreted as the simultaneous absorption or emission of multiple wave quanta. This multi-plasmon damping is of particular interest for highly degenerate electrons, where it can occur on time scales comparable to or shorter than that of linear Landau damping.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2019. p. 47
National Category
Fusion, Plasma and Space Physics
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:umu:diva-162465 (URN)978-91-7855-102-6 (ISBN)
Public defence
2019-09-13, N 420, Naturvetarhuset, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2019-08-23 Created: 2019-08-20 Last updated: 2019-08-21Bibliographically approved

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Brodin, GertEkman, RobinZamanian, Jens

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