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Title: RESISTIVE MAGNETOHYDRODYNAMIC SIMULATIONS OF RELATIVISTIC MAGNETIC RECONNECTION

Abstract

Resistive relativistic magnetohydrodynamic (RRMHD) simulations are applied to investigate the system evolution of relativistic magnetic reconnection. A time-split Harten-Lan-van Leer method is employed. Under a localized resistivity, the system exhibits a fast reconnection jet with an Alfvenic Lorentz factor inside a narrow Petschek-type exhaust. Various shock structures are resolved in and around the plasmoid such as the post-plasmoid vertical shocks and the 'diamond-chain' structure due to multiple shock reflections. Under a uniform resistivity, Sweet-Parker-type reconnection slowly evolves. Under a current-dependent resistivity, plasmoids are repeatedly formed in an elongated current sheet. It is concluded that the resistivity model is of critical importance for RRMHD modeling of relativistic magnetic reconnection.

Authors:
; ;  [1]
  1. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
21451070
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 716; Journal Issue: 2; Other Information: DOI: 10.1088/2041-8205/716/2/L214
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; MAGNETIC RECONNECTION; MAGNETOHYDRODYNAMICS; RELATIVISTIC RANGE; SIMULATION; ENERGY RANGE; FLUID MECHANICS; HYDRODYNAMICS; MECHANICS; PHYSICS

Citation Formats

Zenitani, Seiji, Hesse, Michael, and Klimas, Alex, E-mail: Seiji.Zenitani-1@nasa.go. RESISTIVE MAGNETOHYDRODYNAMIC SIMULATIONS OF RELATIVISTIC MAGNETIC RECONNECTION. United States: N. p., 2010. Web. doi:10.1088/2041-8205/716/2/L214.
Zenitani, Seiji, Hesse, Michael, & Klimas, Alex, E-mail: Seiji.Zenitani-1@nasa.go. RESISTIVE MAGNETOHYDRODYNAMIC SIMULATIONS OF RELATIVISTIC MAGNETIC RECONNECTION. United States. doi:10.1088/2041-8205/716/2/L214.
Zenitani, Seiji, Hesse, Michael, and Klimas, Alex, E-mail: Seiji.Zenitani-1@nasa.go. Sun . "RESISTIVE MAGNETOHYDRODYNAMIC SIMULATIONS OF RELATIVISTIC MAGNETIC RECONNECTION". United States. doi:10.1088/2041-8205/716/2/L214.
@article{osti_21451070,
title = {RESISTIVE MAGNETOHYDRODYNAMIC SIMULATIONS OF RELATIVISTIC MAGNETIC RECONNECTION},
author = {Zenitani, Seiji and Hesse, Michael and Klimas, Alex, E-mail: Seiji.Zenitani-1@nasa.go},
abstractNote = {Resistive relativistic magnetohydrodynamic (RRMHD) simulations are applied to investigate the system evolution of relativistic magnetic reconnection. A time-split Harten-Lan-van Leer method is employed. Under a localized resistivity, the system exhibits a fast reconnection jet with an Alfvenic Lorentz factor inside a narrow Petschek-type exhaust. Various shock structures are resolved in and around the plasmoid such as the post-plasmoid vertical shocks and the 'diamond-chain' structure due to multiple shock reflections. Under a uniform resistivity, Sweet-Parker-type reconnection slowly evolves. Under a current-dependent resistivity, plasmoids are repeatedly formed in an elongated current sheet. It is concluded that the resistivity model is of critical importance for RRMHD modeling of relativistic magnetic reconnection.},
doi = {10.1088/2041-8205/716/2/L214},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 716,
place = {United States},
year = {Sun Jun 20 00:00:00 EDT 2010},
month = {Sun Jun 20 00:00:00 EDT 2010}
}
  • Magnetic reconnection is thought to be the primary mode by which the solar wind couples to the terrestrial magnetosphere, driving phenomena such as magnetic storms and aurorae. While the theory of two-dimensional reconnection is well developed and has been applied with great success to axisymmetric and toroidal systems such as laboratory plasma experiments and fusion devices, it is difficult to justify the application of two-dimensional theory to nontoroidal plasma systems such as Earth's magnetosphere. Unfortunately, the theory of three-dimensional magnetic reconnection is much less well developed, and even defining magnetic reconnection has turned out to be controversial. In this paper,more » recent progress in the use of magnetohydrodynamics (MHD) to address the physics of three-dimensional reconnection in Earth's magnetosphere is reviewed. The paper consists of two parts. In the first part, various definitions of three-dimensional reconnection are reviewed, with the goal of mapping these definitions to sets of physical phenomena that have been identified as 'reconnection' in various contexts. In the second part of the paper, MHD simulation results for the magnetosphere are presented, and two qualitatively distinct types of reconnection phenomena are identified: (1) Steady separator reconnection under generic northward interplanetary magnetic field (IMF) conditions, involving plasma flow across magnetic separatrices, and (2) time-dependent reconnection under generic southward IMF conditions, involving a locally detectable change in the magnetic field topology. It is concluded that magnetic reconnection phenomena at Earth's dayside magnetopause are adequately captured by two distinct definitions: The Vasyliunas definition [V. M. Vasyliunas, Rev. Geophys 13, 303 (1975)], which identifies magnetic reconnection with plasma flow across magnetic separatrices, and the Greene definition [J. Greene, Phys. Fluids B 5, 2355 (1993)], which identifies magnetic reconnection with a violation of magnetic flux conservation. Further generalizations of the definition of magnetic reconnection - e.g., the Schindler-Hesse [K. Schindler and M. Hesse, J. Geophys. Res. 93, 5547 (1988)] definition, which identifies reconnection with spatially localized violations of ideal MHD - are, while potentially useful in characterizing reconnection phenomena in the absence of magnetic nulls, separators, or separatrices, unnecessary in the magnetospheric context.« less
  • To investigate the impact of current sheet motion on the reconnection process, we perform resistive magnetohydrodynamic simulations of two closely located reconnection sites that move apart from each other as reconnection develops. This simulation develops less quickly than an otherwise equivalent single perturbation simulation but eventually exhibits a higher reconnection rate. The unobstructed outflow jets are faster and longer than the outflow jets directed toward the magnetic island that forms between the two current sheets. The X-line and flow stagnation point are located near the trailing end of each current sheet very close to the obstructed exit. The speed ofmore » X-line retreat ranges from {approx}0.02-0.06, while the speed of stagnation point retreat ranges from {approx}0.03-0.07 in units of the initial upstream Alfven velocity. Early in time, the flow stagnation point is located closer to the center of the current sheet than the X-line, but later on the relative positions of these two points switch. Consequently, late in time, there is significant plasma flow across the X-line in the opposite direction of X-line retreat. Throughout the simulation, the velocity at the X-line does not equal the velocity of the X-line. Motivated by these results, an expression for the rate of X-line retreat is derived in terms of local parameters evaluated at the X-line. This expression shows that X-line retreat is due to both advection by the bulk plasma flow and diffusion of the normal component of the magnetic field.« less
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