scholarly journals A two-fluid study of oblique tearing modes in a force-free current sheet

2016 ◽  
Vol 23 (1) ◽  
pp. 012112 ◽  
Author(s):  
Cihan Akçay ◽  
William Daughton ◽  
Vyacheslav S. Lukin ◽  
Yi-Hsin Liu
Keyword(s):  
Current Sheet ◽  
Tearing Modes ◽  
Free Current ◽  
Two Fluid

Obliquely propagating generalized lower-hybrid drift instability with nonlocal two-fluid theory in current sheet equilibrium

2010 ◽  
Vol 17 (10) ◽  
pp. 102102 ◽  
Author(s):  
Dandan Zou ◽  
Weihong Yang ◽  
Yinhua Chen ◽  
P. H. Yoon
Keyword(s):  
Current Sheet ◽  
Lower Hybrid ◽  
Fluid Theory ◽  
Drift Instability ◽  
Two Fluid

scholarly journals Collisionless distribution functions for force-free current sheets: using a pressure transformation to lower the plasma beta

2018 ◽  
Vol 84 (3) ◽  
Author(s):  
F. Wilson ◽  
T. Neukirch ◽  
O. Allanson
Keyword(s):  
Distribution Function ◽  
Current Sheet ◽  
Plasma Phys ◽  
Distribution Functions ◽  
Hermite Functions ◽  
Slow Convergence ◽  
Nonlinear Force ◽  
Free Current ◽  
Transformed Distribution ◽  
General Method

So far, only one distribution function giving rise to a collisionless nonlinear force-free current sheet equilibrium allowing for a plasma beta less than one is known (Allansonet al.,Phys. Plasmas, vol. 22 (10), 2015, 102116; Allansonet al.,J. Plasma Phys., vol. 82 (3), 2016a, 905820306). This distribution function can only be expressed as an infinite series of Hermite functions with very slow convergence and this makes its practical use cumbersome. It is the purpose of this paper to present a general method that allows us to find distribution functions consisting of a finite number of terms (therefore easier to use in practice), but which still allow for current sheet equilibria that can, in principle, have an arbitrarily low plasma beta. The method involves using known solutions and transforming them into new solutions using transformations based on taking integer powers ($N$) of one component of the pressure tensor. The plasma beta of the current sheet corresponding to the transformed distribution functions can then, in principle, have values as low as$1/N$. We present the general form of the distribution functions for arbitrary$N$and then, as a specific example, discuss the case for$N=2$in detail.

scholarly journals Collapse of the neutral current sheet and reconnection at micro-scales

2008 ◽  
Vol 74 (2) ◽  
pp. 215-232 ◽  
Author(s):  
I. F. SHAIKHISLAMOV
Keyword(s):  
Current Sheet ◽  
Large Scale ◽  
Numerical Solutions ◽  
Neutral Current ◽  
Static Solution ◽  
New Process ◽  
Maximum Current ◽  
Nonlinear Static ◽  
Field Lines ◽  
Two Fluid

AbstractReconnection physics at micro-scales is investigated in an electron magnetohydrodynamics frame. A new process of collapse of the neutral current sheet is demonstrated by means of analytical and numerical solutions. It shows how at scales smaller than ion inertia length a compression of the sheet triggers an explosive evolution of current perturbation. Collapse results in the formation of a intense sub-sheet and then an X-point structure embedded into the equilibrium sheet. Hall currents associated with this structure support high reconnection rates. Nonlinear static solution at scales of the electron skin reveals that electron inertia and small viscosity provide an efficient mechanism of field lines breaking. The reconnection rate does not depend on the actual value of viscosity, while the maximum current is found to be restricted even for space plasmas with extremely rare collisions. The results obtained are verified by a two-fluid large-scale numerical simulation.

Structure of a singly ionizing current sheet propagating in a low density gas

1970 ◽  
Vol 48 (15) ◽  
pp. 1769-1780 ◽  
Author(s):  
G. J. Pert
Keyword(s):  
Steady State ◽  
Current Sheet ◽  
Electric Fields ◽  
Mean Free Path ◽  
Transverse Magnetic ◽  
Low Density ◽  
Free Model ◽  
Ionization Region ◽  
Electron Mean Free Path ◽  
Two Fluid

The structure of a singly ionizing current sheet is examined under steady-state conditions. Convergent solutions are only found in the presence of ambient transverse magnetic and electric fields. A collision-free model is used to approximate to the ionization region in the front. This solution is cut off at the electron mean free path and matched to a collision-dominated magnetohydrodynamic two-fluid calculation for the back of the sheet. The conditions for the establishment of a steady state are examined for these solutions.

Linear tearing modes of a forced current-sheet equilibrium

1990 ◽  
Vol 353 ◽  
pp. 658 ◽  
Author(s):  
Paulett C. Liewer ◽  
David G. Payne
Keyword(s):  
Current Sheet ◽  
Tearing Modes

scholarly journals Effect of guide field on three-dimensional electron shear flow instabilities in electron current sheets

2015 ◽  
Vol 81 (6) ◽  
Author(s):  
Neeraj Jain ◽  
Jörg Büchner
Keyword(s):  
Shear Flow ◽  
Current Sheet ◽  
Three Dimensional ◽  
Sheet Thickness ◽  
Electron Current ◽  
Tearing Mode ◽  
Current Sheets ◽  
Tearing Modes ◽  
Guide Field ◽  
Half Thickness

We examine, in the limit of electron plasma ${\it\beta}_{e}\ll 1$, the effect of an external guide field and current sheet thickness on the growth rates and nature of three-dimensional (3-D) unstable modes of an electron current sheet driven by electron shear flow. The growth rate of the fastest growing mode drops rapidly with current sheet thickness but increases slowly with the strength of the guide field. The fastest growing mode is tearing type only for thin current sheets (half-thickness ${\approx}d_{e}$, where $d_{e}=c/{\it\omega}_{pe}$ is the electron inertial length) and zero guide field. For finite guide field or thicker current sheets, the fastest growing mode is a non-tearing type. However, growth rates of the fastest 2-D tearing and 3-D non-tearing modes are comparable for thin current sheets ($d_{e}<\text{half thickness}<2\,d_{e}$) and small guide field (of the order of the asymptotic value of the component of magnetic field supporting the electron current sheet). It is shown that the general mode resonance conditions for tearing modes depend on the effective dissipation mechanism. The usual tearing mode resonance condition ($\boldsymbol{k}\boldsymbol{\cdot }\boldsymbol{B}_{0}=0$, $\boldsymbol{k}$ is the wavevector and $\boldsymbol{B}_{0}$ is the equilibrium magnetic field) can be recovered from the general resonance conditions in the limit of weak dissipation. The conditions (relating current sheet thickness, strength of the guide field and wavenumbers) for the non-existence of tearing mode are obtained from the general mode resonance conditions. We discuss the role of electron shear flow instabilities in magnetic reconnection.

scholarly journals Interaction of multiple magnetic islands in a long current sheet: Two-fluid simulations

2010 ◽  
Vol 37 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
T. K. M. Nakamura ◽  
M. Fujimoto ◽  
H. Sekiya
Keyword(s):  
Current Sheet ◽  
Magnetic Islands ◽  
Two Fluid

Quasilinear saturation of forced current sheet tearing modes

1990 ◽  
Vol 17 (11) ◽  
pp. 2047-2050 ◽  
Author(s):  
Paulett C. Liewer ◽  
David G. Payne
Keyword(s):  
Current Sheet ◽  
Tearing Modes
Sign in / Sign up

Export Citation Format

Share Document