Anomalous transport properties associated with the lower-hybrid-drift instability

Davidson, Ronald C.; Gladd, N. T.

doi:10.1063/1.861021

Cited by 304 publications

(213 citation statements)

References 11 publications

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“…The anomalous transport properties of the LHDI have been of great interest in the theoretical literature, especially as applied to theta pinches [27] and magnetic reconnection [28].…”

Section: Saturation Mechanismsmentioning

confidence: 99%

Experimental study of lower-hybrid drift turbulence in a reconnecting current sheet

Carter

Kulsrud

et al. 2002

Physics of Plasmas

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The role of turbulence in the process of magnetic reconnection has been the subject of a great deal of study and debate in the theoretical literature. At issue in this debate is whether turbulence is essential for fast magnetic reconnection to occur in collisionless current sheets. Some theories claim it is necessary in order to provide anomalous resistivity, while others present a laminar fast reconnection mechanism based on the Hall term in the generalized Ohm's law. In this work, a thorough study of electrostatic potential fluctuations in the current sheet of the Magnetic Reconnection Experiment (MRX) [M. Yamada et al., Phys. Plasmas 4, 1936(1997] was performed in order to ascertain the importance of turbulence in a laboratory reconnection experiment. Using amplified floating Langmuir probes, broadband fluctuations in the lower hybrid frequency range (f LH ∼ 5−15 MHz) were measured which arise with the formation of the current sheet in MRX. The frequency spectrum, spatial amplitude profile, and spatial correlation characteristics of the measured turbulence were examined carefully, finding consistency with theories of the lower-hybrid drift instability (LHDI). The LHDI and its role in magnetic reconnection has been studied theoretically for decades, but this work represents the first detection and detailed study of the LHDI in a laboratory current sheet. The observation of the LHDI in MRX has provided the unique opportunity to uncover the role of this instability in collisionless reconnection. It was found that:(1) the LHDI fluctuations are confined to the low-beta edge of current sheets in MRX; (2) the LHDI amplitude does not correlate well in time or space with the reconnection electric field, which is directly related to the rate of reconnection; and (3) significant LHDI amplitude persists in highcollisionality current sheets where the reconnection rate is classical. These findings suggest that the measured LHDI fluctuations do not play an essential role in determining the reconnection rate in MRX.

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“…The anomalous transport properties of the LHDI have been of great interest in the theoretical literature, especially as applied to theta pinches [27] and magnetic reconnection [28].…”

Section: Saturation Mechanismsmentioning

confidence: 99%

Experimental study of lower-hybrid drift turbulence in a reconnecting current sheet

Carter

Kulsrud

et al. 2002

Physics of Plasmas

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“…One instability which has been extensively investigated theoretically in the context of current sheets is the lower-hybrid drift instability. 28,7 It is a high frequency (⍀ i Ӷ Ӷ⍀ e ) mode driven unstable by cross-field current and associated density gradients, and it persists in the regime T e ՇT i as required in MRX. The mode is strongly growing in i -scale density gradients and has a wavelength near the electron gyroradius and a phase velocity near the ion thermal speed.…”

Section: B Possible Ion Heating Mechanismsmentioning

confidence: 99%

Experimental study of ion heating and acceleration during magnetic reconnection

et al. 2001

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Ion heating and acceleration has been studied in the well-characterized reconnection layer of the Magnetic Reconnection Experiment ͓M. Yamada et al., Phys. Plasmas 4, 1936 ͑1997͔͒. Ion temperature in the layer rises substantially during null-helicity reconnection in which reconnecting field lines are anti-parallel. The plasma outflow is sub-Alfvénic due to a downstream back pressure. An ion energy balance calculation based on the data and including classical viscous heating indicates that ions are heated largely via nonclassical mechanisms. The T i rise is much smaller during co-helicity reconnection in which field lines reconnect obliquely. This is consistent with a slower reconnection rate and a smaller resistivity enhancement over the Spitzer value. These observations show that nonclassical dissipation mechanisms can play an important role both in heating the ions and in facilitating the reconnection process.

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“…The implosion phase of a slow rising reversed field theta-pinch was investigated with magnetic probe measurements and 1 1 2 -D computer simulation of a hybrid code. The initial bias field intensity was between 0.8 and 1.2 kG in hydrogen plasma generated with gas pressure between 45 and 150 mTorr.…”

Section: Discussionmentioning

confidence: 99%

“…The numerical code used is a version of 1 1 2 dimension (space-time, r-t) hybrid code AURORA with inclusion of an electron impact ionization model. The model assumes two bound states n ¼ 1 and n ¼ 2 and the continuum (n !…”

Section: Numerical Simulationmentioning

confidence: 99%

“…On early simulations, the evolution of lower hybrid drift instability (LH) showed to be adequate to explain the smooth radial profile of the magnetic field in the current sheath during the implosion phase of theta-pinches. [1][2][3] Later studies have indicated that this instability is stabilized by finite beta and, therefore, should concentrate only at periphery of the current layer in a field reversed configuration (FRC). 4,5 Experimentally, no evidence of LH was observed in a FRC by CO 2 heterodyne scattering, even in low beta region at edge of configuration.…”

Section: Introductionmentioning

confidence: 99%

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Resistivity in the dynamic current sheath of a field reversed configuration

Kayama

2012

Physics of Plasmas

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The resistivity of a field reversed configuration in a theta-pinch with slow rising current was investigated during the turbulent phase from the moment of field reversal until end of plasma radial implosion. This transport coefficient was obtained in a hydrogen plasma by local measurements with magnetic probe and compared to numerical calculations with Chodura resistivity and evolution of lower hybrid drift instability. The values of resistivity are higher than those predicted by classical binary collision. During early phase of confinement, the doubly layer structure of current sheath in the low electric field machine was theoretically well reproduced with anomalous collision frequency calculated with Chodura resistivity that provides appropriate conditions for onset of lower hybrid drift instability and the regular evolution of pinch. The plasma dynamic, radial profiles of magnetic field during the radial compression and resistivity values were equally close to those observed by the measurements. V C 2012 American Institute of Physics. [http://dx

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Anomalous transport properties associated with the lower-hybrid-drift instability

Cited by 304 publications

References 11 publications

Experimental study of lower-hybrid drift turbulence in a reconnecting current sheet

Experimental study of lower-hybrid drift turbulence in a reconnecting current sheet

Experimental study of ion heating and acceleration during magnetic reconnection

Resistivity in the dynamic current sheath of a field reversed configuration

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