scholarly journals Reduced models accounting for parallel magnetic perturbations: gyrofluid and finite Larmor radius–Landau fluid approaches

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
E. Tassi ◽  
P. L. Sulem ◽  
T. Passot
Keyword(s):  
Fluid Model ◽  
Collisionless Plasma ◽  
Low Frequency ◽  
Wave Model ◽  
Plasma Phys ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Closure Relation ◽  
Reduced Models ◽  
Finite Larmor Radius

Reduced models are derived for a strongly magnetized collisionless plasma at scales which are large relative to the electron thermal gyroradius and in two asymptotic regimes. One corresponds to cold ions and the other to far sub-ion scales. By including the electron pressure dynamics, these models improve the Hall reduced magnetohydrodynamics (MHD) and the kinetic Alfvén wave model of Boldyrev et al. (2013 Astrophys. J., vol. 777, 2013, p. 41), respectively. We show that the two models can be obtained either within the gyrofluid formalism of Brizard (Phys. Fluids, vol. 4, 1992, pp. 1213–1228) or as suitable weakly nonlinear limits of the finite Larmor radius (FLR)–Landau fluid model of Sulem and Passot (J. Plasma Phys., vol 81, 2015, 325810103) which extends anisotropic Hall MHD by retaining low-frequency kinetic effects. It is noticeable that, at the far sub-ion scales, the simplifications originating from the gyroaveraging operators in the gyrofluid formalism and leading to subdominant ion velocity and temperature fluctuations, correspond, at the level of the FLR–Landau fluid, to cancellation between hydrodynamic contributions and ion finite Larmor radius corrections. Energy conservation properties of the models are discussed and an explicit example of a closure relation leading to a model with a Hamiltonian structure is provided.

scholarly journals Alfvén wave filamentation and dispersive phase mixing in a high-density channel: Landau fluid and hybrid simulations

2009 ◽  
Vol 16 (2) ◽  
pp. 275-285 ◽  
Author(s):  
D. Borgogno ◽  
P. Hellinger ◽  
T. Passot ◽  
P. L. Sulem ◽  
P. M. Trávníček
Keyword(s):  
Fluid Model ◽  
Collisionless Plasma ◽  
Density Perturbation ◽  
High Density ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Plasma Parameters ◽  
Phase Mixing ◽  
Finite Larmor Radius ◽  
Dispersive Phase

Abstract. The propagation of dispersive Alfvén waves in a low-beta collisionless plasma with a high-density channel aligned with the ambient magnetic field, is studied in three space dimensions. A fluid model retaining linear Landau damping and finite Larmor radius corrections is used, together with a hybrid particle-in-cell simulation aimed to validate the predictions of this Landau-fluid model. It is shown that when the density enhancement is moderate (depending on the pump wavelength and the plasma parameters), the wave energy concentrates into a filament whose transverse size is prescribed by the dimension of the channel. In contrast, in the case of a stronger density perturbation, the early formation of a magnetic filament is followed by the onset of thin helical ribbons and the development of strong gradients. This "dispersive phase mixing" provides a mechanism permitting dissipation processes (not included in the present model) to act and heat the plasma.

scholarly journals Landau fluid closures with nonlinear large-scale finite Larmor radius corrections for collisionless plasmas

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
P. L. Sulem ◽  
T. Passot
Keyword(s):  
Large Scale ◽  
Fluid Model ◽  
Low Frequency ◽  
Larmor Radius ◽  
Large Temperature ◽  
Ion Cyclotron Resonance ◽  
Finite Larmor Radius ◽  
Collisionless Plasmas ◽  
Kinetic Effects ◽  
Linear Kinetic Theory

With the aim to develop a tool for simulating turbulence in collisionless magnetized plasmas, fluid models retaining low-frequency kinetic effects such as Landau damping and finite Larmor radius (FLR) corrections are discussed. It turns out that, in the absence of ion-cyclotron resonance, the dispersion and damping of kinetic Alfvén waves at scales as small as a fraction of the ion Larmor radius are accurately reproduced when using fluid estimates of the non-gyrotropic moments, at leading-order within a large-scale asymptotics. Differently, evaluations based on the low-frequency linear kinetic theory are necessary in regimes of large temperature anisotropies, and in particular in the presence of the mirror instability. Combining both descriptions leads to a new Landau fluid model retaining large-scale FLR nonlinearities, while reproducing the linear dynamics of low-frequency modes at the sub-ionic scales.

Fluid model of collisionless plasma with finite Larmor radius effects

1995 ◽  
Vol 2 (12) ◽  
pp. 4451-4454 ◽  
Author(s):  
A. I. Smolyakov ◽  
I. O. Pogutse ◽  
A. Hirose
Keyword(s):  
Fluid Model ◽  
Collisionless Plasma ◽  
Larmor Radius ◽  
Finite Larmor Radius

Evolution of nonlinear Alfvén waves propagating along the magnetic field in a collisionless plasma

1982 ◽  
Vol 28 (3) ◽  
pp. 459-468 ◽  
Author(s):  
M. Khanna ◽  
R. Rajaram
Keyword(s):  
Magnetic Field ◽  
Collisionless Plasma ◽  
Momentum Equation ◽  
Finite Amplitude ◽  
Alfven Wave ◽  
Mhd Waves ◽  
Larmor Radius ◽  
Finite Larmor Radius ◽  
Flr Effects ◽  
The Magnetic Field

It is shown that the asymptotic evolution of a finite-amplitude Alfvén wave propagating parallel to the uniform magnetic field in a warm homogeneous collisionless plasma is governed by the modified nonlinear Schrödinger equation. The dispersion is provided by the ion finite Larmor radius (FLR) effects in the momentum equation and the Hall current and electron pressure corrections to the generalized Ohm's law. In the cold plasma limit the equations reduce to those available in the literature. It is suggested that these calculations can have a bearing on the investigation of the structure of MHD waves in the solar wind.

scholarly journals A fluid description for Landau damping of dispersive MHD waves

2004 ◽  
Vol 11 (2) ◽  
pp. 245-258 ◽  
Author(s):  
T. Passot ◽  
P. L. Sulem
Keyword(s):  
Fluid Model ◽  
Collisionless Plasma ◽  
Alfven Waves ◽  
Landau Damping ◽  
Mhd Waves ◽  
Larmor Radius ◽  
Alfvén Waves ◽  
Weakly Nonlinear ◽  
Linear Character ◽  
Finite Larmor Radius

Abstract. The dynamics of long oblique MHD waves in a collisionless plasma permeated by a uniform magnetic field is addressed using a Landau-fluid model that includes Hall effect and electron-pressure gradient in a generalized Ohm's law and retains ion finite Larmor radius (FLR) corrections to the gyrotropic pressure (Phys. Plasmas 10, 3906, 2003). This one-fluid model, built to reproduce the weakly nonlinear dynamics of long dispersive Alfvén waves propagating along an ambient field, is shown to correctly capture the Landau damping of oblique magnetosonic waves predicted by a kinetic theory based on the Vlasov-Maxwell system. For oblique and kinetic Alfvén waves (for which second order FLR corrections are to be retained), the linear character of waves with small but finite amplitudes is established, and the dispersion relation reproduced in the regime of adiabatic protons and isothermal electrons, associated with the condition me/mp

scholarly journals A two-fluid model describing the finite-collisionality, stationary Alfvén wave in anisotropic plasma

2008 ◽  
Vol 15 (6) ◽  
pp. 957-964 ◽  
Author(s):  
S. M. Finnegan ◽  
M. E. Koepke ◽  
D. J. Knudsen
Keyword(s):  
Fluid Model ◽  
Collisionless Plasma ◽  
Alfven Wave ◽  
Temperature Anisotropy ◽  
Thermal Pressure ◽  
Exclusion Region ◽  
Two Fluid Model ◽  
The Magnetic Field ◽  
Range Of Values ◽  
Two Fluid

Abstract. The stationary inertial Alfvén (StIA) wave (Knudsen, 1996) was predicted for cold, collisionless plasma. The model was generalized (Finnegan et al., 2008) to include nonzero values of electron and ion collisional resistivity and thermal pressure. Here, the two-fluid model is further generalized to include anisotropic thermal pressure. A bounded range of values of parallel electron drift velocity is found that excludes periodic stationary Alfvén wave solutions. This exclusion region depends on the value of the local Alfvén speed VA, plasma beta perpendicular to the magnetic field β⊥ and electron temperature anisotropy.

scholarly journals Magnetic holes in plasmas close to the mirror instability

2007 ◽  
Vol 14 (4) ◽  
pp. 373-383 ◽  
Author(s):  
D. Borgogno ◽  
T. Passot ◽  
P. L. Sulem
Keyword(s):  
Numerical Simulations ◽  
Fluid Model ◽  
Instability Threshold ◽  
Landau Damping ◽  
Larmor Radius ◽  
Maxwell System ◽  
Unstable Regime ◽  
Finite Larmor Radius ◽  
Spatio Temporal ◽  
Hall Mhd

Abstract. Non-propagating magnetic hole solutions in anisotropic plasmas near the mirror instability threshold are investigated in numerical simulations of a fluid model that incorporates linear Landau damping and finite Larmor radius corrections calculated in the gyrokinetic approximation. This FLR-Landau fluid model reproduces the subcritical mirror bifurcation recently identified on the Vlasov-Maxwell system, both by theory and numerics. Stable magnetic hole solutions that display a polarization different from that of Hall-MHD solitons are indeed obtained slighlty below threshold, while magnetic patterns and spatio-temporal chaos emerge when the system is maintained in a mirror unstable regime.

scholarly journals Plasma Heating by Alfvén Waves - Kinetic Properties of Magnetohydrodynamic Disturbances

1985 ◽  
Vol 107 ◽  
pp. 381-389
Author(s):  
Akira Hasegawa
Keyword(s):  
Electric Field ◽  
Plasma Heating ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Alfvén Waves ◽  
Kinetic Properties ◽  
Parallel Electric Field ◽  
Astrophysical Plasmas ◽  
Finite Larmor Radius ◽  
Wave Heating

Mechanisms of Alfvén wave heating in space-astrophysical plasmas are presented with particular emphasis on the parallel electric field generated in the magnetohydrodynamic perturbations due to the finite Larmor radius effects.

scholarly journals Finite-Larmor-radius equilibrium and currents of the Earth’s flank magnetopause

2018 ◽  
Vol 84 (5) ◽  
Author(s):  
S. S. Cerri
Keyword(s):  
Fluid Model ◽  
Larmor Radius ◽  
Anisotropic Pressure ◽  
Current Layer ◽  
Ion Dynamics ◽  
Finite Larmor Radius ◽  
Analytic Expressions ◽  
The One ◽  
Flr Effects ◽  
The Magnetic Field

We consider the one-dimensional equilibrium problem of a shear-flow boundary layer within an ‘extended-fluid model’ of a plasma that includes the Hall and the electron pressure terms in Ohm’s law, as well as dynamic equations for anisotropic pressure for each species and first-order finite-Larmor-radius (FLR) corrections to the ion dynamics. We provide a generalized version of the analytic expressions for the equilibrium configuration given in Cerri et al., (Phys. Plasmas, vol. 20 (11), 2013, 112112), highlighting their intrinsic asymmetry due to the relative orientation of the magnetic field $\boldsymbol{B}$, $\boldsymbol{b}=\boldsymbol{B}/|\boldsymbol{B}|$, and the fluid vorticity $\unicode[STIX]{x1D74E}=\unicode[STIX]{x1D735}\times \boldsymbol{u}$ (‘$\unicode[STIX]{x1D74E}\boldsymbol{b}$ asymmetry’). Finally, we show that FLR effects can modify the Chapman–Ferraro current layer at the flank magnetopause in a way that is consistent with the observed structure reported by Haaland et al., (J. Geophys. Res. (Space Phys.), vol. 119, 2014, pp. 9019–9037). In particular, we are able to qualitatively reproduce the following key features: (i) the dusk–dawn asymmetry of the current layer, (ii) a double-peak feature in the current profiles and (iii) adjacent current sheets having thicknesses of several ion Larmor radii and with different current directions.

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