Finite Larmor radius influence on MHD solitary waves

Mjølhus, E.

doi:10.5194/npg-16-251-2009

Cited by 8 publications

(10 citation statements)

References 23 publications

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“…and p ⊥ /(ρ|B|) = const., see e.g. Mjølhus (2009). Additionally, similarly to the definition of (appropriately normalized) entropy in MHD, s = ln(p/ρ γ ), it is useful to define parallel and perpendicular entropy in the CGL model, according to…”

Section: On the Paper Bymentioning

confidence: 99%

An introductory guide to fluid models with anisotropic temperatures. Part 1. CGL description and collisionless fluid hierarchy

et al. 2019

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We present a detailed guide to advanced collisionless fluid models that incorporate kinetic effects into the fluid framework, and that are much closer to the collisionless kinetic description than traditional magnetohydrodynamics. Such fluid models are directly applicable to modelling the turbulent evolution of a vast array of astrophysical plasmas, such as the solar corona and the solar wind, the interstellar medium, as well as accretion disks and galaxy clusters. The text can be viewed as a detailed guide to Landau fluid models and it is divided into two parts. Part 1 is dedicated to fluid models that are obtained by closing the fluid hierarchy with simple (non-Landau fluid) closures. Part 2 is dedicated to Landau fluid closures. Here in Part 1, we discuss the fluid model of Chew–Goldberger–Low (CGL) in great detail, together with fluid models that contain dispersive effects introduced by the Hall term and by the finite Larmor radius corrections to the pressure tensor. We consider dispersive effects introduced by the non-gyrotropic heat flux vectors. We investigate the parallel and oblique firehose instability, and show that the non-gyrotropic heat flux strongly influences the maximum growth rate of these instabilities. Furthermore, we discuss fluid models that contain evolution equations for the gyrotropic heat flux fluctuations and that are closed at the fourth-moment level by prescribing a specific form for the distribution function. For the bi-Maxwellian distribution, such a closure is known as the ‘normal’ closure. We also discuss a fluid closure for the bi-kappa distribution. Finally, by considering one-dimensional Maxwellian fluid closures at higher-order moments, we show that such fluid models are always unstable. The last possible non Landau fluid closure is therefore the ‘normal’ closure, and beyond the fourth-order moment, Landau fluid closures are required.

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Section: On the Paper Bymentioning

confidence: 99%

An introductory guide to fluid models with anisotropic temperatures. Part 1. CGL description and collisionless fluid hierarchy

et al. 2019

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“…which contribute to the evolution of the pressure tensor by involving only B, u and Q, respectively (∂/∂t + u · ∇ has been replaced by the Lagrangian time derivative d/dt for † For a derivation based on a perturbative expansion of the distribution function, see Macmahon (1965) or Schekochihin et al (2010). Other classical derivations can be found in Yajima (1966), Ramos (2005b) or in Mjølhus (2009). ‡ We normalize all the quantities with respect to the mass, m, the thermal speed, v th , and a reference density and magnetic field, n0 and B0, respectively: n = n0 n, B = B0 B, u = v th u, Π = mn0v 2 th Π, and Q = mn0v 3 th Q.…”

Section: B1 Perturbative Expansion Of the Pressure Tensor Equationmentioning

confidence: 99%

“…(2010). Other classical derivations can be found in Yajima (1966), Ramos (2005 b ) or in Mjølhus (2009).…”

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confidence: 99%

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

Cerri

2018

J. Plasma Phys.

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We consider the one-dimensional equilibrium problem of a shear-flow boundary layer within an "extended fluid model" of plasma that includes the Hall and the electron pressure terms in the 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. (2013), highlighting their intrinsic asymmetry due to the relative orientation of the magnetic field b = B/|B| and the fluid vorticity ω = ∇ × u ("ωb 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. (2014). 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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“…As shown in Ref. 30, the addition of finite Larmor radius is rather challenging because it prevent an explicit relation between the magnetic field and the normal velocity plasma components (Eqs. (10) and (11)).…”

Section: Intermediate Shock Wavesmentioning

confidence: 99%

Structure of intermediate shocks in collisionless anisotropic Hall-magnetohydrodynamics plasma models

Sánchez‐Arriaga

2013

Physics of Plasmas

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The existence of discontinuities within the double-adiabatic Hall-magnetohydrodynamics (MHD) model is discussed. These solutions are transitional layers where some of the plasma properties change from one equilibrium state to another. Under the assumption of traveling wave solutions with velocity C and propagation angle h with respect to the ambient magnetic field, the Hall-MHD model reduces to a dynamical system and the waves are heteroclinic orbits joining two different fixed points. The analysis of the fixed points rules out the existence of rotational discontinuities. Simple considerations about the Hamiltonian nature of the system show that, unlike dissipative models, the intermediate shock waves are organized in branches in parameter space, i.e., they occur if a given relationship between h and C is satisfied. Electron-polarized (ion-polarized) shock waves exhibit, in addition to a reversal of the magnetic field component tangential to the shock front, a maximum (minimum) of the magnetic field amplitude. The jumps of the magnetic field and the relative specific volume between the downstream and the upstream states as a function of the plasma properties are presented. The organization in parameter space of localized structures including in the model the influence of finite Larmor radius is discussed. V

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Finite Larmor radius influence on MHD solitary waves

Cited by 8 publications

References 23 publications

An introductory guide to fluid models with anisotropic temperatures. Part 1. CGL description and collisionless fluid hierarchy

An introductory guide to fluid models with anisotropic temperatures. Part 1. CGL description and collisionless fluid hierarchy

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

Structure of intermediate shocks in collisionless anisotropic Hall-magnetohydrodynamics plasma models

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