scholarly journals Landau damping in one dimensional periodic inhomogeneous collisionless plasmas

AIP Advances ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 025229
Author(s):  
Sanjeev Kumar Pandey ◽  
Rajaraman Ganesh
Keyword(s):  
Landau Damping ◽  
One Dimensional ◽  
Collisionless Plasmas

scholarly journals Fluidization of collisionless plasma turbulence

2019 ◽  
Vol 116 (4) ◽  
pp. 1185-1194 ◽  
Author(s):  
Romain Meyrand ◽  
Anjor Kanekar ◽  
William Dorland ◽  
Alexander A. Schekochihin
Keyword(s):  
Solar Wind ◽  
Power Law ◽  
Collisionless Plasma ◽  
Plasma Turbulence ◽  
Magnetized Plasma ◽  
Landau Damping ◽  
Astrophysical Plasmas ◽  
Phase Mixing ◽  
Fluid Turbulence ◽  
Collisionless Plasmas

In a collisionless, magnetized plasma, particles may stream freely along magnetic field lines, leading to “phase mixing” of their distribution function and consequently, to smoothing out of any “compressive” fluctuations (of density, pressure, etc.). This rapid mixing underlies Landau damping of these fluctuations in a quiescent plasma—one of the most fundamental physical phenomena that makes plasma different from a conventional fluid. Nevertheless, broad power law spectra of compressive fluctuations are observed in turbulent astrophysical plasmas (most vividly, in the solar wind) under conditions conducive to strong Landau damping. Elsewhere in nature, such spectra are normally associated with fluid turbulence, where energy cannot be dissipated in the inertial-scale range and is, therefore, cascaded from large scales to small. By direct numerical simulations and theoretical arguments, it is shown here that turbulence of compressive fluctuations in collisionless plasmas strongly resembles one in a collisional fluid and does have broad power law spectra. This “fluidization” of collisionless plasmas occurs, because phase mixing is strongly suppressed on average by “stochastic echoes,” arising due to nonlinear advection of the particle distribution by turbulent motions. Other than resolving the long-standing puzzle of observed compressive fluctuations in the solar wind, our results suggest a conceptual shift for understanding kinetic plasma turbulence generally: rather than being a system where Landau damping plays the role of dissipation, a collisionless plasma is effectively dissipationless, except at very small scales. The universality of “fluid” turbulence physics is thus reaffirmed even for a kinetic, collisionless system.

scholarly journals Electron acceleration by a localized electric field

1986 ◽  
Vol 4 (3-4) ◽  
pp. 439-452 ◽  
Author(s):  
D. Galmiche ◽  
J. P. Nicolle ◽  
D. Pesme
Keyword(s):  
Particle Acceleration ◽  
Electric Field ◽  
Plasma Wave ◽  
Electron Acceleration ◽  
Landau Damping ◽  
One Dimensional ◽  
Convective Regime ◽  
Electric Structure ◽  
Electron Distributions

The acceleration of test electrons by a resonant, one—dimensional electric structure is studied in the convective regime with the Zakharov equations. Depending on the nonlinearity level the particle acceleration is due to diffusion or trapping by the plasma wave. Electron distributions are obtained and compared with 1-D particle code results. Influence of Landau damping formulation is discussed.

Relaxation of collisionless plasmas

1994 ◽  
Vol 51 (2) ◽  
pp. 341-353 ◽  
Author(s):  
H. Wiechen ◽  
H. J. Ziegler
Keyword(s):  
Phase Space ◽  
Point Of View ◽  
Coarse Grained ◽  
Second Step ◽  
Final States ◽  
General Technique ◽  
One Dimensional ◽  
Collisionless Plasmas ◽  
Mixing Dynamics ◽  
Stable Equilibria

We present a new theory for the relaxation of two-dimensional collisionless quasi-neutral plasmas by mixing in phase space. In general, mixing in phase space does not lead to equilibrium states in the framework of exact, collisionless theory. However, filamentation on smaller and smaller scales can result in stationary states from a macroscopic (coarse-grained) point of view. In a first step we discuss a general technique to calculate suitably stable equilibria of collisionless plasmas. In a second step we develop a model relaxation that yields a simple transition to a description on macroscopic scales without following the details of the complicated mixing dynamics. Combination of both results allows calculation of final states of collisionless relaxation. We illustrate our approach with the help of a one-dimensional sheet configuration as a simple example.

scholarly journals Fluid simulations of non-resonant anisotropic ion heating

2013 ◽  
Vol 31 (7) ◽  
pp. 1195-1204 ◽  
Author(s):  
D. Laveder ◽  
T. Passot ◽  
P. L. Sulem
Keyword(s):  
Fluid Model ◽  
Dominant Role ◽  
Heat Fluxes ◽  
Landau Damping ◽  
Larmor Radius ◽  
Ion Heating ◽  
Thermal Dynamics ◽  
Dominant Type ◽  
Finite Larmor Radius ◽  
Collisionless Plasmas

Abstract. The finite Larmor radius (FLR)-Landau fluid model, which extends the usual anisotropic magnetohydrodynamics to magnetized collisionless plasmas by retaining linear Landau damping and finite Larmor radius corrections down to the sub-ionic scales in the quasi-transverse directions, is used to study the non-resonant heating of the plasma by randomly driven Alfvén waves. One-dimensional numerical simulations, free from any artificial dissipation, are used to analyze the influence on the thermal dynamics, of the beta parameter and of the separation between the driving and the ion scales. While the gyrotropic heat fluxes play a dominant role when the plasma is driven at large scales, leading to a parallel heating of the ions by Landau damping, a different regime develops when the driving acts at scales comparable to the ion Larmor radius. Perpendicular heating and parallel cooling of the ions are then observed, an effect that is mostly due to the work of the non-gyrotropic pressure force and that can be viewed as the fluid signature of the so-called stochastic heating. A partial characterization of the plasma by global quantities (such as the magnetic compressibility and the density-magnetic field correlations that provide information on the dominant type of waves) is also presented. The enhancement of the parallel electron heating by a higher level of fast magnetosonic waves is in particular pointed out.

scholarly journals Одномерное квазилинейное уравнение для описания генерации токов увлечения в плазме токамака геликонами

2022 ◽  
Vol 48 (2) ◽  
pp. 24
Author(s):  
А.Ю. Попов ◽  
Е.З. Гусаков
Keyword(s):  
Distribution Function ◽  
Diffusion Coefficient ◽  
Linear Equation ◽  
Electron Distribution ◽  
Electron Distribution Function ◽  
Planck Equation ◽  
Electron Velocity ◽  
Landau Damping ◽  
One Dimensional ◽  
Dimensional Equation

A quasi-linear equation which allows describing evolution of electron distribution function and generation of non-inductive currents by helicons is obtained. It is shown that in the analysed case the Fokker-Planck equation can be approximated by a one-dimensional equation in the longitudinal electron velocity space with a diffusion coefficient proportional to the helicon power absorbed by electrons due to Landau damping.

Adaptive Multi-Physics Simulations of Collisionless Plasmas

2021 ◽  
Author(s):  
Simon Lautenbach ◽  
Rainer Grauer
Keyword(s):  
Magnetic Reconnection ◽  
Vlasov Equation ◽  
Fluid Model ◽  
Environmental Modeling ◽  
Landau Damping ◽  
Proof Of Concept ◽  
Collisionless Plasmas ◽  
Space Environments ◽  
Small Parts ◽  
Kinetic Treatment

<p>Collisionless plasmas, mostly present in astrophysical and space environments, often require a kinetic treatment given by the Vlasov equation. Unfortunately, the six-dimensional Vlasov equation is inherently expensive to compute and usually can only be solved on very small parts of the considered spatial domain. However, in some cases, e.g. magnetic reconnection, it is sufficient to solve the Vlasov equation in a localized domain and solve the remaining domain with appropriate fluid models. We present an adaptive hierarchical treatment of collisionless plasmas ranging from fully kinetic, to a 10-moment fluid model incorporating a simplified treatment of Landau damping, to a 5-moment fluid description. To account for separation of electron and ion physics, hybrid stages of mixed electron and ion models are also allowed. As a proof of concept, the full physics-adaptive hierarchy is applied to the Geospace Environmental Modeling (GEM) challenge of magnetic reconnection.</p>

Numerische Integration der nichtlinearen Vlasov-Gleichung

1961 ◽  
Vol 16 (12) ◽  
pp. 1320-1328 ◽  
Author(s):  
G. Knorr
Keyword(s):  
Electric Field ◽  
Electric Energy ◽  
Landau Damping ◽  
Collision Term ◽  
Dimensional Electron ◽  
Initial Value ◽  
Linear Solution ◽  
One Dimensional ◽  
Trapped Particles ◽  
Linear Effect

The VLASOV equation, i. e. the BOLTZMANN equation without collision term, was numerically integrated as an initial value problem together with the second MAXWELL equation for a one-dimensional electron plasma with smeared-out ion background. The initial values were taken as a MAXWELLian distribution in velocity space and a cosine distribution in position, resulting in a sinusform for the electric field.The LANDAU damping of the total energy of the electric field turned out to be valid for times larger than those given by a formal estimation of the validity of the linear solution. For still later times, the decay rate of the electric energy is less than that given by LANDAU damping.The period of validity of LANDAU damping was computed by estimating the influence of the trapped particles. As a non-linear effect the first harmonic of the electric field builds up within this period. The growth of the first harmonic is faster for larger wave numbers k.

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