scholarly journals Anisotropic pressure and finite hot-electron Larmor-radius effects on ring stability

1982 ◽  
Author(s):  
K. T. Tsang ◽  
X. S. Lee ◽  
P. J. Catto
Keyword(s):  
Larmor Radius ◽  
Anisotropic Pressure ◽  
Hot Electron ◽  
Ring Stability

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.

The effects of finite Larmor radius on the perturbation flow mixing of a collisionless plasma

1970 ◽  
Vol 4 (2) ◽  
pp. 403-424 ◽  
Author(s):  
Shigeki Morioka ◽  
John R. Spreiter
Keyword(s):  
Mach Number ◽  
Collisionless Plasma ◽  
Distribution Functions ◽  
Larmor Radius ◽  
Anisotropic Pressure ◽  
Finite Larmor Radius ◽  
Flow Mixing ◽  
Linearized Problem ◽  
Velocity Distribution Functions ◽  
Low Theory

The Chew—Goldberger—Low theory of a collisionless plasma, modified to include the effect of finite Larmor radius of the ion and the electron, is applied to a linearized problem of two-dimensional steady flow. The zeroth-order terms in the Larmor radius expansions of the velocity distribution functions of the ion and the electron are assumed to be anisotropic Maxwellian. The spatial development of a given velocity profile is investigated for flows with either crossed or aligned magnetic fields, and for various values of Mach number, Alfvén Mach number, and anisotropic pressure ratios in the main flow.

On the stability of the screw pinch in the CGL model

1976 ◽  
Vol 16 (3) ◽  
pp. 261-283 ◽  
Author(s):  
Krishna M. Srivastava ◽  
F. Waelbroeck
Keyword(s):  
Magnetic Field ◽  
Wave Number ◽  
Larmor Radius ◽  
Anisotropic Pressure ◽  
Finite Larmor Radius ◽  
Main Column ◽  
First Order Correction ◽  
The Stability ◽  
The Magnetic Field ◽  
Ideal Plasma

We have investigated the stability of the screw pinch with the help of the double adiabatic (CGL) equations including the finite Larmor radius effects through the anisotropic pressure tensor. The calculations are approximate, with FLR treated as a first-order correction to the ideal plasma equations. The dispersion relation has been solved for various values of R2 = p∥/p⊥ and α for the rale and imaginary part of the frequency (ω = ωR ± iωI) in three particular cases: (a) μ = 0, the θ-pinch, (b) μ = ∞, the Z-pinch, (c) μ = -α/m, field distubances parallel to the equilibrium field. Here μ is the pitch of the magnetic field in the pressureless plasma surrounding the main column, α is the wave number, m is the azimuthal number, p∥ and p⊥ are plasma pressures along and perpendicular to the magnetic field.

scholarly journals Electron-scale reduced fluid models with gyroviscous effects

2017 ◽  
Vol 83 (4) ◽  
Author(s):  
T. Passot ◽  
P. L. Sulem ◽  
E. Tassi
Keyword(s):  
Magnetic Energy ◽  
Pressure Fluctuations ◽  
Transverse Magnetic ◽  
Larmor Radius ◽  
Anisotropic Pressure ◽  
Turbulence Energy ◽  
Fluid Models ◽  
Magnetic Fluctuations ◽  
Pressure Balance ◽  
Finite Larmor Radius

Reduced fluid models for collisionless plasmas including electron inertia and finite Larmor radius corrections are derived for scales ranging from the ion to the electron gyroradii. Based either on pressure balance or on the incompressibility of the electron fluid, they respectively capture kinetic Alfvén waves (KAWs) or whistler waves (WWs), and can provide suitable tools for reconnection and turbulence studies. Both isothermal regimes and Landau fluid closures permitting anisotropic pressure fluctuations are considered. For small values of the electron beta parameter $\unicode[STIX]{x1D6FD}_{e}$, a perturbative computation of the gyroviscous force valid at scales comparable to the electron inertial length is performed at order $O(\unicode[STIX]{x1D6FD}_{e})$, which requires second-order contributions in a scale expansion. Comparisons with kinetic theory are performed in the linear regime. The spectrum of transverse magnetic fluctuations for strong and weak turbulence energy cascades is also phenomenologically predicted for both types of waves. In the case of moderate ion to electron temperature ratio, a new regime of KAW turbulence at scales smaller than the electron inertial length is obtained, where the magnetic energy spectrum decays like $k_{\bot }^{-13/3}$, thus faster than the $k_{\bot }^{-11/3}$ spectrum of WW turbulence.

Magnetic-field generation in laser fusion and hot-electron transport

1986 ◽  
Vol 64 (8) ◽  
pp. 912-919 ◽  
Author(s):  
M. G. Haines
Keyword(s):  
Magnetic Field ◽  
Electron Transport ◽  
Diffusion Processes ◽  
Anisotropic Pressure ◽  
Laser Fusion ◽  
Hot Electron ◽  
Magnetic Field Generation ◽  
Dynamo Action ◽  
The Many ◽  
Many Sources

The many sources of generation of magnetic field are derived from a generalized Ohm's law. These sources include the [Formula: see text] effect, anisotropic pressure, as well as the effect of the quiver velocity associated with the incident laser beam. The magnetic field can be generated either through some imposed lack of spherical symmetry or through an instability. Among the latter, the collisional Weibel instability appears to be the most important. Convection and amplification can occur through the Nernst effect, and the resulting magnetic-field structure can inhibit fast-electron transport. Dynamo action and diffusion processes are also included in this review.

The scaling of collisionless magnetic reconnection in an electron–positron plasma with non-scalar pressure

2012 ◽  
Vol 79 (5) ◽  
pp. 473-477 ◽  
Author(s):  
M. HOSSEINPOUR ◽  
M. A. MOHAMMADI ◽  
S. BIABANI
Keyword(s):  
Magnetic Reconnection ◽  
Skin Depth ◽  
Larmor Radius ◽  
Anisotropic Pressure ◽  
Diffusion Region ◽  
Pair Plasma ◽  
Tearing Instability ◽  
Electron Positron ◽  
Sheet Width ◽  
Field Lines

AbstractCollisionless magnetic reconnection via tearing instability in non-relativistic electron–positron (pair) plasma with an anisotropic pressure is investigated. The equilibrium magnetic field is considered to be sheared force-free, and a set of linearized collisionless Magnetohydrodynamics equations describes the evolution of reconnection dynamics. A linear analytical analysis, based on scaling, demonstrates that in such a pair plasma, breaking the frozen in flow constraint for field lines can be mainly provided by the non-gyrotropic pressure of electrons and positrons (rather than the particle bulk inertia) when the current sheet width is smaller than the particle Larmor radius (Δx < rL). This condition is satisfied when β > d2 (d = c/ωp is the particle skin-depth with the electron/positron frequency ωp and β = 8πP(0)/B02 ⪡ 1). Meanwhile, on top of the Lorentz force and in the absence of the reconnection facilitating mechanism of the Hall effect, non-scalar pressure force can accelerate bulk plasma into the diffusion region at the scale lengths of the order of dx. Therefore, the respective regime of tearing instability proceeds much faster compared with the case of an isotropic pressure with a new dimensionless growth rate of (γτA) ~ d.

Magnetogravitational instability of a rotating anisotropic plasma with finite-ion-Larmor-radius corrections and generalized polytropic laws

1998 ◽  
Vol 60 (4) ◽  
pp. 673-694 ◽  
Author(s):  
G. D. SONI ◽  
R. K. CHHAJLANI
Keyword(s):  
Magnetic Field ◽  
Electrical Resistivity ◽  
Dispersion Relation ◽  
Normal Mode Analysis ◽  
Transverse Mode ◽  
Mode Analysis ◽  
Larmor Radius ◽  
Anisotropic Pressure ◽  
Axis Of Rotation ◽  
The Magnetic Field

The gravitational instability of an infinite homogeneous, finitely conducting, rotating, collisionless, anisotropic-pressure plasma in the presence of a uniform magnetic field with finite-ion-Larmor-radius (FLR) corrections and generalized polytropic laws is investigated. The polytropic laws are considered for the pressure components in directions parallel and perpendicular to the magnetic field. The method of normal-mode analysis is applied to derive the dispersion relation. Wave propagation is considered for both parallel and perpendicular axes of rotation. Longitudinal and transverse modes of propagation are discussed separately. The effects of rotation, finite electrical resistivity, FLR corrections and polytropic indices on the gravitational, firehose and mirror instabilities are discussed. The stability of the system is discussed by applying the Routh–Hurwitz criterion. Extensive numerical treatment of the dispersion relation leads to several interesting results. For the transverse mode of propagation with the axis of rotation parallel to the magnetic field, it is observed that rotation stabilizes the system by decreasing the critical Jeans wavenumber. It is also seen that the region of instability and the value of the critical Jeans wavenumber are larger for the Chew–Goldberger–Low (CGL) set of equations in comparison with the magnetohydrodynamic (MHD) set of equations. It is found that the effect of FLR corrections is significant only in the low-wavelength range, and produces a stabilizing influence. For the transverse mode of propagation with the axis of rotation parallel to the magnetic field, the finite electrical resistivity removes the polytropic index [nu] from the condition for instability. The inclusion of rotation alone or FLR corrections alone or both together does not affect the condition for mirror instability. The growth rate of the mirror instability is modified owing to uniform rotation or FLR corrections or both together. We note that the condition of mirror instability depends upon the polytropic indices. We also note that neither the mirror instability nor the firehose instability can be observed for the isotropic MHD set of equations.

scholarly journals Hot Accretion Flow in Two-Dimensional Spherical Coordinates: Considering Pressure Anisotropy and Magnetic Field

Universe ◽  
2019 ◽  
Vol 5 (9) ◽  
pp. 197
Author(s):  
Hui-Hong Deng ◽  
De-Fu Bu
Keyword(s):  
Magnetic Field ◽  
Mhd Equations ◽  
Larmor Radius ◽  
Anisotropic Pressure ◽  
Strong Wind ◽  
Two Dimensional ◽  
Spherical Coordinates ◽  
Gas Temperature ◽  
Accretion Flow ◽  
Anisotropic Stress

For systems with extremely low accretion rate, such as Galactic Center Sgr A* and M87 galaxy, the ion collisional mean free path can be considerably larger than its Larmor radius. In this case, the gas pressure is anisotropic to magnetic field lines. In this paper, we pay attention to how the properties of outflow change with the strength of anisotropic pressure and the magnetic field. We use an anisotropic viscosity to model the anisotropic pressure. We solve the two-dimensional magnetohydrodynamic (MHD) equations in spherical coordinates and assume that the accretion flow is radially self-similar. We find that the work done by anisotropic pressure can heat the accretion flow. The gas temperature is heightened when anisotropic stress is included. The outflow velocity increases with the enhancement of strength of the anisotropic force. The Bernoulli parameter does not change much when anisotropic pressure is involved. However, we find that the energy flux of outflow can be increased by a factor of 20 in the presence of anisotropic stress. We find strong wind (the mass outflow is about 70% of the mass inflow rate) is formed when a relatively strong magnetic field is present. Outflows from an active galactic nucleus can interact with gas in its host galaxies. Our result predicts that outflow feedback effects can be enhanced significantly when anisotropic pressure and a relatively powerful magnetic field is considered.

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