Current sheet formation at a magnetic neutral line in Hall magnetohydrodynamics

2007 ◽  
Vol 14 (11) ◽  
pp. 112303 ◽  
Author(s):  
Yuri E. Litvinenko
Keyword(s):  
Current Sheet ◽  
Neutral Line ◽  
Magnetic Neutral Line

scholarly journals Hall MHD and Electron Inertia Effects in Current Sheet Formation at a Magnetic Neutral Line

2015 ◽  
Vol 5 (2) ◽  
pp. 109-125 ◽  
Author(s):  
Yuri E. Litvinenko ◽  
Liam C. McMahon
Keyword(s):  
Current Sheet ◽  
Finite Time ◽  
Numerical Solutions ◽  
Neutral Line ◽  
Singularity Formation ◽  
Time Singularity ◽  
Similarity Reduction ◽  
Electron Inertia ◽  
Magnetic Neutral Line ◽  
Finite Time Singularity

AbstractAn exact self-similar solution is used to investigate current sheet formation at a magnetic neutral line in incompressible Hall magnetohydrodynamics. The collapse to a current sheet is modelled as a finite-time singularity in the solution for electric current density at the neutral line. We establish that a finite-time collapse to the current sheet can occur in Hall magnetohydrodynamics, and we find a criterion for the finite-time singularity in terms of the initial conditions. We derive an asymptotic solution for the singularity formation and a formula for the singularity formation time. The analytical results are illustrated by numerical solutions, and we also investigate an alternative similarity reduction. Finally, we generalise our solution to incorporate resistive, viscous and electron inertia terms.

scholarly journals Statistical visualization of the Earth's magnetotail based on Geotail data and the implied substorm model

2009 ◽  
Vol 27 (3) ◽  
pp. 1035-1046 ◽  
Author(s):  
S. Machida ◽  
Y. Miyashita ◽  
A. Ieda ◽  
M. Nosé ◽  
D. Nagata ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Plasma Sheet ◽  
Neutral Line ◽  
Substorm Onset ◽  
Start Time ◽  
Superposed Epoch Analysis ◽  
Central Plasma ◽  
Magnetic Neutral Line

Abstract. We investigated the temporal and spatial development of the near-Earth magnetotail during substorms based on multi-dimensional superposed-epoch analysis of Geotail data. The start time of the auroral break-up (t=0) of each substorm was determined from auroral data obtained by the Polar and IMAGE spacecraft. The key parameters derived from the plasma, magnetic-field, and electric-field data from Geotail were sorted by their meridional X(GSM)–Z(proxy) coordinates. The results show that the Poynting flux toward the plasma-sheet center starts at least 10 min before the substorm onset, and is further enhanced at X~−12 RE (Earth radii) around 4 min before the onset. Simultaneously, large-amplitude fluctuations occurred, and earthward flows in the central plasma sheet between X~−11 RE and X~−19 RE and a duskward flow around X=−10 RE were enhanced. The total pressure starts to decrease around X=−16 RE about 4 min before the onset of the substorm. After the substorm onset, a notable dipolarization is observed and tailward flows commence, characterised by southward magnetic fields in the form of a plasmoid. We confirm various observable-parameter variations based on or predicted by the relevant substorm models; however, none of these can explain our results perfectly. Therefore, we propose a catapult (slingshot) current-sheet relaxation model, in which an earthward convective flow produced by catapult current-sheet relaxation and a converted duskward flow near the Earth are enhanced through flow braking around 4 min before the substorm onset. These flows induce a ballooning instability or other instabilities, causing the observed current disruption. The formation of the magnetic neutral line is a natural consequence of the present model, because the relaxation of a highly stretched catapult current-sheet produces a very thin current at its tailward edge being surrounded by intense earthward and tailward magnetic fields which were formerly the off-equatorial lobe magnetic fields. This location is the boundary between a highly stressed catapult current sheet and a Harris-type current sheet characterized by little stress. In addition, the flows induced around the boundary toward the current-sheet center may enhance the formation of the magnetic neutral line and the efficiency of magnetic reconnection. After magnetic reconnection is induced, it plays a significant role in driving the substorm.

scholarly journals Vector Magnetic Fields at the Base of Filaments and the Filament Environment

1998 ◽  
Vol 167 ◽  
pp. 98-101 ◽  
Author(s):  
Jingxiu Wang ◽  
Wei Li
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Field Gradient ◽  
Neutral Line ◽  
Transverse Field ◽  
Line Of Sight ◽  
Horizontal Gradient ◽  
Major Fraction ◽  
Flux System ◽  
Magnetic Neutral Line

AbstractBased on an analysis of three active filaments in AR 6891, we find that vector magnetic fields at the base of filaments and the filament environment is characterized by the following: (1) The transverse field is parallel along the magnetic neutral line for most of the filaments. The average transverse field beneath the filaments is more than 400 G. (2) The horizontal gradient of the line-of-sight field crossing the neutral line is, more or less, constant along the major fraction of a filament, but very steep at the two ends. The average gradient is 0.06 G/km. (3) For each of the filaments there is a squeezing magnetic structure which represents an intrusion of a satellite bipole into the main flux system. The neutral line for a squeezing magnetic structure has a large curvature, a strong sheared transverse field of more than 1 KG, and a steep field gradient of approximate 0.3 G/km. (4) The transverse field and field gradient are clearly enhanced before the filament eruption.

scholarly journals Properties of Magnetic Neutral Line Gradients and Formation of Filaments

Solar Physics ◽  
2013 ◽  
Vol 289 (3) ◽  
pp. 821-830 ◽  
Author(s):  
Nina V. Karachik ◽  
Alexei A. Pevtsov
Keyword(s):  
Neutral Line ◽  
Magnetic Neutral Line
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