Enhancement of the guide field during the current sheet formation in the three-dimensional magnetic configuration with an X line

2009 ◽  
Vol 373 (16) ◽  
pp. 1460-1464 ◽  
Author(s):  
Anna Frank ◽  
Sergey Bugrov ◽  
Vladimir Markov
Keyword(s):  
Current Sheet ◽  
Three Dimensional ◽  
Magnetic Configuration ◽  
Guide Field

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 Numerical study of the reconnection process between magnetic cloud and heliospheric current sheet

2018 ◽  
Vol 619 ◽  
pp. A82
Author(s):  
Man Zhang ◽  
Yu Fen Zhou ◽  
Xue Shang Feng ◽  
Bo Li ◽  
Ming Xiong
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Dynamic Process ◽  
Large Scale ◽  
Magnetic Cloud ◽  
Numerical Study ◽  
Three Dimensional ◽  
Heliospheric Current Sheet ◽  
Reconnection Process ◽  
Magnetic Filed

In this paper, we have used a three-dimensional numerical magnetohydrodynamics model to study the reconnection process between magnetic cloud and heliospheric current sheet. Within a steady-state heliospheric model that gives a reasonable large-scale structure of the solar wind near solar minimum, we injected a spherical plasmoid to mimic a magnetic cloud. When the magnetic cloud moves to the heliospheric current sheet, the dynamic process causes the current sheet to become gradually thinner and the magnetic reconnection begin. The numerical simulation can reproduce the basic characteristics of the magnetic reconnection, such as the correlated/anticorrelated signatures in V and B passing a reconnection exhaust. Depending on the initial magnetic helicity of the cloud, magnetic reconnection occurs at points along the boundary of the two systems where antiparallel field lines are forced together. We find the magnetic filed and velocity in the MC have a effect on the reconnection rate, and the magnitude of velocity can also effect the beginning time of reconnection. These results are helpful in understanding and identifying the dynamic process occurring between the magnetic cloud and the heliospheric current sheet.

scholarly journals Filaments and striations: anisotropies in observed, supersonic, highly magnetized turbulent clouds

2019 ◽  
Vol 492 (1) ◽  
pp. 668-685 ◽  
Author(s):  
James R Beattie ◽  
Christoph Federrath
Keyword(s):  
Magnetic Field ◽  
Column Density ◽  
Three Dimensional ◽  
High Density ◽  
Systematic Analysis ◽  
Guide Field ◽  
Degree Of Anisotropy ◽  
Mach Numbers ◽  
Magnetohydrodynamic Simulations ◽  
The Magnetic Field

ABSTRACT Stars form in highly magnetized, supersonic turbulent molecular clouds. Many of the tools and models that we use to carry out star formation studies rely upon the assumption of cloud isotropy. However, structures like high-density filaments in the presence of magnetic fields and magnetosonic striations introduce anisotropies into the cloud. In this study, we use the two-dimensional power spectrum to perform a systematic analysis of the anisotropies in the column density for a range of Alfvén Mach numbers ($\operatorname{\mathcal {M}_{\text{A}}}=0.1{\!-\!10}$) and turbulent Mach numbers ($\operatorname{\mathcal {M}}=2{\!-\!20}$), with 20 high-resolution, three-dimensional turbulent magnetohydrodynamic simulations. We find that for cases with a strong magnetic guide field, corresponding to $\operatorname{\mathcal {M}_{\text{A}}}\lt 1$, and $\operatorname{\mathcal {M}}\lesssim 4$, the anisotropy in the column density is dominated by thin striations aligned with the magnetic field, while for $\operatorname{\mathcal {M}}\gtrsim 4$ the anisotropy is significantly changed by high-density filaments that form perpendicular to the magnetic guide field. Indeed, the strength of the magnetic field controls the degree of anisotropy and whether or not any anisotropy is present, but it is the turbulent motions controlled by $\operatorname{\mathcal {M}}$ that determine which kind of anisotropy dominates the morphology of a cloud.

Three-dimensional modeling of electron quasiviscous dissipation in guide-field magnetic reconnection

2005 ◽  
Vol 12 (10) ◽  
pp. 100704 ◽  
Author(s):  
Michael Hesse ◽  
Masha Kuznetsova ◽  
Karl Schindler ◽  
Joachim Birn
Keyword(s):  
Magnetic Reconnection ◽  
Three Dimensional ◽  
Three Dimensional Modeling ◽  
Guide Field ◽  
Dimensional Modeling

scholarly journals 3D turbulent reconnection driven current-sheet dynamics: solar applications

2010 ◽  
Vol 6 (S274) ◽  
pp. 458-460
Author(s):  
Lapo Bettarini ◽  
Giovanni Lapenta
Keyword(s):  
Current Sheet ◽  
Characteristic Time ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Anomalous Effect ◽  
Instability Modes ◽  
Diffusive Dynamics ◽  
Three Dimensional Configuration ◽  
A Current ◽  
Dimensional Picture

AbstractWe provide a complete three-dimensional picture of the reconnecting dynamics of a current-sheet. Recently, a two-dimensional non-steady reconnection dynamics has been proved to occur without the presence of any anomalous effect (Lapenta, 2008, Skender & Lapenta, 2010, Bettarini & Lapenta, 2010) but such a picture must be confirmed in a full three-dimensional configuration wherein all instability modes are allowed to drive the evolution of the system, i.e. to sustain a reconnection dynamics or to push the system along a different instability path. Here we propose a full-space analysis allowing us to determine the longitudinal and, possibly, the transversal modes driving the different current-sheet disruption regimes, the corresponding characteristic time-scales and to study system's instability space- parameter (plasma beta, Lundquist and Reynolds numbers, system's aspect ratio). The conditions leading to an explosive evolution rather then to a diffusive dynamics as well as the details of the reconnection inflow/outflow regime at the disruption phase are determined. Such system embedded in a solar-like environment and undergoing a non-steady reconnection evolution may determine the formation both of jets and waves influencing the dynamics and energetic of the upper layers and of characteristic down-flows as observed in the low solar atmosphere.

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