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Studies of non-MHD effects during ma...

Ren, Yang.

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Studies of non-MHD effects during magnetic reconnection in a laboratory plasma.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Studies of non-MHD effects during magnetic reconnection in a laboratory plasma./
Author:	Ren, Yang.
Description:	186 p.
Notes:	Adviser: Masaaki Yamada.
Contained By:	Dissertation Abstracts International68-01B.
Subject:	Physics, Fluid and Plasma. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3250026

Studies of non-MHD effects during magnetic reconnection in a laboratory plasma.
Ren, Yang.

Studies of non-MHD effects during magnetic reconnection in a laboratory plasma. - 186 p.

Adviser: Masaaki Yamada.

Thesis (Ph.D.)--Princeton University, 2007.

In this dissertation we present studies of non-MHD effects, the Hall effect and magnetic fluctuations, during magnetic reconnection in the laboratory plasma of the Magnetic Reconnection Experiment (MRX). The Hall effect is studied by measuring its key signature, an out-of-plane quadrupole magnetic field, with magnetic probe arrays whose spatial resolution is on the order of the electron skin depth. The in-plane electron flow is calculated from out-of-plane magnetic field measurements. The measured in-plane electron flow and predictions from numerical simulations are in good agreement. The electron diffusion region is identified by measuring the electron outflow channel. The width of the electron diffusion region scales with the electron skin depth, and the electron outflow velocity scales with the electron Alfven velocity. In contrast to simulations, the presence of classical and anomalous dissipation broadens the electron diffusion region and slows the electron outflow. The electron outflow flux is independent of the width of the electron diffusion region. The ions, as measured by a Mach probe, have a much wider outflow channel than the electrons, and their outflow is much slower than the electron outflow everywhere in the electron diffusion region. The separatrices are identified by tracing the ridges of the measured quadrupole field. The angle between the two separatrices defines the aspect ratio of the ion diffusion region, which shows a positive correlation with the aspect ratio of the electron diffusion region. Further measurements show that, in the collisionless regime, the Hall effect balances the reconnecting electric field at the electron diffusion region edge and correlates with the measured effective resistivity. Magnetic fluctuations and the quadrupole field are simultaneously measured in the diffusion region during collisionless magnetic reconnection. The presence of both non-MHD effects shows that the development of plasma turbulence, a three-dimensional feature, does not disrupt the generation of the quadrupole field, a two-dimensional feature. Time-frequency analysis shows that these magnetic fluctuations have spectral peaks around the lower-hybrid frequency. The time characteristics of the fluctuations reveal their impulsive nature. The location of peak fluctuations is found to be at the current sheet center at three different positions along the outflow direction.Subjects--Topical Terms:

1018402
Physics, Fluid and Plasma.

Studies of non-MHD effects during magnetic reconnection in a laboratory plasma.
LDR:03253nam 2200253 a 45 001 954202
005 20110621
008 110622s2007 eng d
035 $a (UMI)AAI3250026
035 $a AAI3250026
040 $a UMI $c UMI
100 1 $a Ren, Yang. $3 1277675
245 1 0 $a Studies of non-MHD effects during magnetic reconnection in a laboratory plasma.
300 $a 186 p.
500 $a Adviser: Masaaki Yamada.
500 $a Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0357.
502 $a Thesis (Ph.D.)--Princeton University, 2007.
520 $a In this dissertation we present studies of non-MHD effects, the Hall effect and magnetic fluctuations, during magnetic reconnection in the laboratory plasma of the Magnetic Reconnection Experiment (MRX). The Hall effect is studied by measuring its key signature, an out-of-plane quadrupole magnetic field, with magnetic probe arrays whose spatial resolution is on the order of the electron skin depth. The in-plane electron flow is calculated from out-of-plane magnetic field measurements. The measured in-plane electron flow and predictions from numerical simulations are in good agreement. The electron diffusion region is identified by measuring the electron outflow channel. The width of the electron diffusion region scales with the electron skin depth, and the electron outflow velocity scales with the electron Alfven velocity. In contrast to simulations, the presence of classical and anomalous dissipation broadens the electron diffusion region and slows the electron outflow. The electron outflow flux is independent of the width of the electron diffusion region. The ions, as measured by a Mach probe, have a much wider outflow channel than the electrons, and their outflow is much slower than the electron outflow everywhere in the electron diffusion region. The separatrices are identified by tracing the ridges of the measured quadrupole field. The angle between the two separatrices defines the aspect ratio of the ion diffusion region, which shows a positive correlation with the aspect ratio of the electron diffusion region. Further measurements show that, in the collisionless regime, the Hall effect balances the reconnecting electric field at the electron diffusion region edge and correlates with the measured effective resistivity. Magnetic fluctuations and the quadrupole field are simultaneously measured in the diffusion region during collisionless magnetic reconnection. The presence of both non-MHD effects shows that the development of plasma turbulence, a three-dimensional feature, does not disrupt the generation of the quadrupole field, a two-dimensional feature. Time-frequency analysis shows that these magnetic fluctuations have spectral peaks around the lower-hybrid frequency. The time characteristics of the fluctuations reveal their impulsive nature. The location of peak fluctuations is found to be at the current sheet center at three different positions along the outflow direction.
590 $a School code: 0181.
650 4 $a Physics, Fluid and Plasma. $3 1018402
690 $a 0759
710 2 $a Princeton University. $3 645579
773 0 $t Dissertation Abstracts International $g 68-01B.
790 $a 0181
790 1 0 $a Yamada, Masaaki, $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3250026