The microinstabilities of a high-β plasma flow with a non-uniform velocity profile

1980 ◽  
Vol 24 (3) ◽  
pp. 385-407 ◽  
Author(s):  
A. B. Mikhailovskii ◽  
V. A. Klimenko
Keyword(s):  
Magnetic Field ◽  
High Pressure ◽  
Velocity Profile ◽  
Kinetic Analysis ◽  
Plasma Flow ◽  
Large Family ◽  
Larmor Radius ◽  
Helmholtz Instability ◽  
Uniform Velocity ◽  
Pressure Plasma

The microinstabilities of a high-pressure plasma moving along a magnetic field with a non-uniform velocity profile are investigated. A similar problem was studied earlier by Dobrowolny on the basis of hydromagnetic equations with an oblique viscosity tensor. The present paper, unlike Dobrowolny's work, gives a kinetic analysis. Perturbations with transverse wavelength both larger and smaller than the ion Larmor radius are considered. The analysis indicates that there is a large family of microinstabilities of the ‘drift’ type whose mechanism differs from the classical Kelvin–Helmholtz instability.

scholarly journals Diffusion at the Earth magnetopause: enhancement by Kelvin-Helmholtz instability

2007 ◽  
Vol 25 (1) ◽  
pp. 271-282 ◽  
Author(s):  
R. Smets ◽  
G. Belmont ◽  
D. Delcourt ◽  
L. Rezeau
Keyword(s):  
Magnetic Field ◽  
Distribution Functions ◽  
Larmor Radius ◽  
Simple Analytical Model ◽  
Helmholtz Instability ◽  
Field Reversal ◽  
Finite Larmor Radius ◽  
The Earth ◽  
Specific Distribution ◽  
The Magnetic Field

Abstract. Using hybrid simulations, we examine how particles can diffuse across the Earth's magnetopause because of finite Larmor radius effects. We focus on tangential discontinuities and consider a reversal of the magnetic field that closely models the magnetopause under southward interplanetary magnetic field. When the Larmor radius is on the order of the field reversal thickness, we show that particles can cross the discontinuity. We also show that with a realistic initial shear flow, a Kelvin-Helmholtz instability develops that increases the efficiency of the crossing process. We investigate the distribution functions of the transmitted ions and demonstrate that they are structured according to a D-shape. It accordingly appears that magnetic reconnection at the magnetopause is not the only process that leads to such specific distribution functions. A simple analytical model that describes the built-up of these functions is proposed.

Micro-instabilities due to fast ions in a high pressure plasma in a curved magnetic field

1977 ◽  
Vol 19 (12) ◽  
pp. 1177-1185 ◽  
Author(s):  
B I Meerson ◽  
A B Mikhailovskii ◽  
O A Pokhotelov
Keyword(s):  
Magnetic Field ◽  
High Pressure ◽  
Pressure Plasma ◽  
Fast Ions

Effect of finite ion Larmor radius on the Kelvin–Helmholtz instability

1978 ◽  
Vol 20 (2) ◽  
pp. 149-160 ◽  
Author(s):  
Hirosh Nagano
Keyword(s):  
Magnetic Field ◽  
Flow Velocity ◽  
Wave Vector ◽  
Uniform Magnetic Field ◽  
Critical Value ◽  
Larmor Radius ◽  
Helmholtz Instability ◽  
Finite Larmor Radius ◽  
Compressible Plasma ◽  
The Difference

The effect of finite ion Larmor radius on the Kelvin–Helmholtz instability is investigated in the cases of an incompressible and a compressible plasma. When a wave vector is perpendicular to a uniform magnetic field, the effect of finite Larmor radius (FLR) stabilizes perturbations with a wavenumber exceeding a critical value, while there exists another case that the FLR effect destabilizes still more than the usual MHD approximation. The difference between these cases is decided from the configuration of flow velocity and magnetic field. When a wave vector is parallel to a magnetic field, the FLR effect tends to stabilize perturbations with a larger wavenumber.

Hydromagnetic Kelvin-Heimholtz Instability in the Presence of Suspended Particles and Finite Larmor Radius Effect

1994 ◽  
Vol 49 (12) ◽  
pp. 1102-1110 ◽  
Author(s):  
R. K. Sanghvi ◽  
R. K. Chhajlani
Keyword(s):  
Magnetic Field ◽  
Uniform Magnetic Field ◽  
Suspended Particles ◽  
Linear Analysis ◽  
Wave Number ◽  
Larmor Radius ◽  
Helmholtz Instability ◽  
Finite Larmor Radius ◽  
Simplifying Assumptions ◽  
The Magnetic Field

Abstract A linear analysis of the combined influence of a finite ion Larmor radius and suspended particles on Kelvin-Helmholtz instability in the presence of a uniform magnetic field is carried out. The magnetic field is assumed to be uniform and transverse to the direction of streaming. The medium is assumed to be incompressible. Certain simplifying assumptions are made for the motion of the suspended particles. A dispersion relation for such a medium has been obtained using appropriate boundary conditions. The stabilizing effect of a finite Larmor radius has been reasserted in the absence of the suspended particles. A stability criterion for the medium is derived, which is found to be independent of the presence of the suspended particles. Similarly a condition of instability of the system is also derived. Numerical analysis is presented in a few limiting cases of interest. Furthermore, growth rates of unstable modes of the configuration with increasing relaxation fre­quency of the particles and finite Larmor radius have been evaluated analytically. It is shown that the finite Larmor radius in the presence of the suspended particles destabilizes a certain wave number band which is stable otherwise. Implications of the suspended particles on the growth rate of unstable modes are discussed in the limit of vanishing ion Larmor radius.

Assessments of Magnetic Reconnection and Kelvin-Helmholtz Instability at Ganymede's Upstream Magnetopause

2020 ◽  
Author(s):  
Nawapat Kaweeyanun ◽  
Adam Masters ◽  
Xianzhe Jia
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Larmor Radius ◽  
Helmholtz Instability ◽  
Reconnection Rate ◽  
Permanent Magnetic Field ◽  
Field Orientation ◽  
Finite Larmor Radius ◽  
Energy Flows ◽  
Flr Effects

<p>Ganymede is the largest moon of Jupiter and the only Solar System moon known to generate a permanent magnetic field. Motions of Jupiter’s magnetospheric plasma around Ganymede create an upstream magnetopause, where energy flows are thought to be driven by magnetic reconnection and/or Kelvin-Helmholtz Instability (KHI). Previous numerical simulations of Ganymede indicate evidence for transient reconnection events and KHI wave structures, but the natures of both processes remain poorly understood. Here we present an analytical model of steady-state conditions at Ganymede’s magnetopause, from which we conduct first assessments of reconnection and KHI onset criteria at the boundary. We find that reconnection may occur wherever Ganymede’s closed magnetic field encounters Jupiter’s ambient magnetic field, regardless of variations in magnetopause conditions. Unrestricted reconnection onset highlights possibilities for multiple X-lines or widespread transient reconnection at Ganymede. The reconnection rate is controlled by the ambient Jovian field orientation and hence driven by Jupiter’s rotation. We also determine Ganymede’s magnetopause conditions to be favorable for KHI wave growths in two confined regions each along a magnetopause flank, both of which grow in area whenever Ganymede moves toward Jupiter’s magnetospheric current sheet. KHI growth rates are calculated with the Finite Larmor Radius (FLR) effects incorporated and found to be asymmetric favoring the magnetopause flank closest to Jupiter. The significance of KHI wave growth on energy flows at Ganymede’s magnetopause remains to be investigated. Future progress on both topics is highly relevant for the upcoming JUpiter ICy moon Explorer (JUICE) mission.</p>

Combined Taylor and Helmholtz instability in hydromagnetics including Hall effect

1967 ◽  
Vol 1 (1) ◽  
pp. 145-155 ◽  
Author(s):  
S. P. Talwar ◽  
G. L. Kalra
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Hall Effect ◽  
Uniform Magnetic Field ◽  
Hall Current ◽  
Larmor Frequency ◽  
Larmor Radius ◽  
Helmholtz Instability ◽  
Unstable Configuration

The problem of combined Rayleigh—Taylor and Kelvin—Helmholtz instability for incompressible plasmas carrying a uniform magnetic field is investigated taking account of the Hall current. The resistivity and the finite ion Larmor radius effects are left out. It is found that the finite Larmor frequency is destabilizing in nature. The growth rate of an otherwise (without the Hall current) unstable configuration is increased, and unstable modes may be produced in otherwise stable situations for reasonably large values of the Hall current. The Hall effect also results in overstable modes.

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