Propagation of linear waves in relativistic anisotropic magnetohydrodynamics

Gebretsadkan, W. B.; Kalra, G. L.

doi:10.1103/physreve.66.057401

Cited by 14 publications

(7 citation statements)

References 7 publications

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“…This study adopted a 3 + 1 formalism, which is the one adhered to here as well. It is pointed out how this result fits in the established theoretical framework, and how it can then be used to generalize the findings for linear waves in relativistic anisotropic MHD formulations, 15 with a pressure difference along and perpendicular to the magnetic field. In Sec.…”

Section: Introduction: Relativistic Mhdmentioning

confidence: 89%

“…The fact that pointlike perturbations in stationary plasmas will give group diagrams that can be very demanding on spatial resolution ͑due to the wave aberration effects combined with MHD wave anisotropy͒, is yet again a clear indication that RMHD codes will need some form of grid-adaptivity, to handle complex three-dimensional RMHD astrophysical problems. The linear wave properties discussed here are also relevant to better appreciate the knowledge of discontinuous ͑shock͒ wave solutions allowed by the RMHD equations, 2,3,[19][20][21][22] or the linear wave modifications encountered in fluid models for relativistic plasmas that invoke anisotropic pressure 15 or do not have sufficient collisionality to justify a RMHD viewpoint. 23,24 Finally, knowledge of the wave properties in uniform media is indispensible to appreciate the significant modifications encountered when diagnosing waves and instabilities in nonuniform, relativistic MHD equilibrium configurations.…”

Section: Discussionmentioning

confidence: 99%

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Linear wave propagation in relativistic magnetohydrodynamics

Keppens

Méliani

2008

Physics of Plasmas

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The properties of linear Alfvén, slow, and fast magnetoacoustic waves for uniform plasmas in relativistic magnetohydrodynamics ͑MHD͒ are discussed, augmenting the well-known expressions for their phase speeds with knowledge on the group speed. A 3 + 1 formalism is purposely adopted to make direct comparison with the Newtonian MHD limits easier and to stress the graphical representation of their anisotropic linear wave properties using the phase and group speed diagrams. By drawing these for both the fluid rest frame and for a laboratory Lorentzian frame which sees the plasma move with a three-velocity having an arbitrary orientation with respect to the magnetic field, a graphical view of the relativistic aberration effects is obtained for all three MHD wave families. Moreover, it is confirmed that the classical Huygens construction relates the phase and group speed diagram in the usual way, even for the lab frame viewpoint. Since the group speed diagrams correspond to exact solutions for initial conditions corresponding to a localized point perturbation, their formulae and geometrical construction can serve to benchmark current high-resolution algorithms for numerical relativistic MHD.

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Section: Introduction: Relativistic Mhdmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Linear wave propagation in relativistic magnetohydrodynamics

Keppens

Méliani

2008

Physics of Plasmas

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“…As stated above, this is a new ordering, different from pseudo-MHD(U S < U A < U F < U ST ) and reverse-MHD (U A < U S < U F < U ST ), wherein the Alfvén mode is found to be faster than the fast mode [Gebretsadkan and Kalra, 2002]. In the magnetosheath, plasma beta (b = p/ B 2 8p ) has been found to vary widely and values of the order $10 have been observed [Phan et al, 1994].…”

Section: Propagation In the Magnetosheath Plasmamentioning

confidence: 99%

“…in the above equation, one gets the dispersion relation for relativistic anisotropic MHD (RAM) [Gedalin, 1993;Gebretsadkan and Kalra, 2002]. For g k 1 = 2, g ?…”

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confidence: 99%

Effect of He⁺⁺ ions on the propagation of low‐frequency magnetohydrodynamic waves in the magnetosheath

Kalra

Kumar

2006

J. Geophys. Res.

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[1] The paper investigates the role of suprathermal particles (He ++ ) in the propagation of low-frequency waves in average magnetosheath plasma by utilizing a model which is a concatenation of two magnetohydrodynamic (MHD) fluids. The suprathermal component is described by a relativistic, collisionless anisotropic fluid while the background plasma is assumed to be a nonrelativistic, anisotropic MHD fluid. The pressure components of both the fluids are described by heuristic double-polytropic laws which are fairly well supported by observational data. The linearized analysis is carried out and dispersion relation is derived using normal mode technique. It is found that inclusion of the suprathermal component causes the excitation of an additional mode of propagation, besides reducing the phase speeds of slow, fast, and Alfvén modes. The additional mode, which can be characterized as a hybrid of the suprathermal and the fast modes in the direction perpendicular to the magnetic field, is the only mode which transports energy in the direction perpendicular to the magnetic field. Using appropriate polytropic indices obtained from AMPTE/IRM measurements in the magnetosheath leads to a new ordering of phase speeds and density-magnetic field correlation of the fast mode. The new suprathermal mode shows positive density-magnetic field correlation.

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“…The Chew et al (1956) equations are derived by taking velocity moments of the collisionless Boltzmann transport equation assuming that the thermal heat flow along the field lines can be neglected. Considering the importance of anisotropic pressure plasma, various investigations have been carried out by the authors listed in the references (Gliddon, 1966;Kalra et al, 1970;Kathuria and Kalra, 1973;Chhajlani and Purohit, 1985;Yajima, 1966;Summers, 1978;Ferriere, 2004;Shrauner, 1967;Gedalin, 1993;Gebretsadkan and Kalra, 2002;Ghildyal and Kalra, 1997;Chust and Belmont, 2006), all of them using double adiabatic Chew et al (1956) equations neglecting the heat flux vector.…”

Section: Introductionmentioning

confidence: 99%

Propagation of waves in a gravitating and rotating anisotropic heat conducting plasma

Gebretsadkan¹

2017

mejs

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An inviscid, unbounded, collisionless, gravitating, rotating and heat conducting anisotropic plasma medium which is drifting is considered. The medium is assumed to be embedded in a strong magnetic field. A general dispersion relation is derived using normal mode analysis and its various limiting cases are discussed, compared with similar earlier results for a non-drifting model, and some disagreements are indicated. The dispersion relation reveals the existence of five waves. These different wave modes are discussed in some particular cases analytically. It is found that in the case of parallel propagation all the five waves propagate. When the axis of rotation is across the magnetic field, the modified entropy wave and the modified anisotropic Alfven wave are independent of rotation, gravitation and heat flux. It is shown that the drift velocity has no effect on the stability of these waves but their phase velocities are found to be altered by the drift velocity; the forward propagating modes being increased and the backward modes decreased. The other three waves are affected by gravitation, rotation, drift and parallel component of the heat flux. It is further shown that only two waves propagate in the perpendicular direction. The propagating wave modes in this particular direction are not affected by the drift velocity since wave normal is transverse to the direction of flow.

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Propagation of linear waves in relativistic anisotropic magnetohydrodynamics

Cited by 14 publications

References 7 publications

Linear wave propagation in relativistic magnetohydrodynamics

Linear wave propagation in relativistic magnetohydrodynamics

Effect of He⁺⁺ ions on the propagation of low‐frequency magnetohydrodynamic waves in the magnetosheath

Propagation of waves in a gravitating and rotating anisotropic heat conducting plasma

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Propagation of linear waves in relativistic anisotropic magnetohydrodynamics

Cited by 14 publications

References 7 publications

Linear wave propagation in relativistic magnetohydrodynamics

Linear wave propagation in relativistic magnetohydrodynamics

Effect of He++ ions on the propagation of low‐frequency magnetohydrodynamic waves in the magnetosheath

Propagation of waves in a gravitating and rotating anisotropic heat conducting plasma

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Effect of He⁺⁺ ions on the propagation of low‐frequency magnetohydrodynamic waves in the magnetosheath