Sub-Alfvénic velocity limits in magnetohydrodynamic rotating plasmas

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https://pubs.aip.org/aip/pop/article-abstract/17/5/052503/920544/Sub-Alfvenic-velocity-limits-in?redirectedFrom=fulltext

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https://doi.org/10.1063/1.3383051
 http://hdl.handle.net/11603/31454

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UMBC Mechanical Engineering Department

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Author/Creator ORCID

https://orcid.org/0000-0002-6830-3126

Date

2010-05-14

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journal articles
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Citation of Original Publication

C. Teodorescu, R. Clary, R. F. Ellis, A. B. Hassam, C. A. Romero-Talamas, W. C. Young; Sub-Alfvénic velocity limits in magnetohydrodynamic rotating plasmas. Phys. Plasmas 1 May 2010; 17 (5): 052503. https://doi.org/10.1063/1.3383051

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This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in C. Teodorescu, R. Clary, R. F. Ellis, A. B. Hassam, C. A. Romero-Talamas, W. C. Young; Sub-Alfvénic velocity limits in magnetohydrodynamic rotating plasmas. Phys. Plasmas 1 May 2010; 17 (5): 052503. https://doi.org/10.1063/1.3383051 and may be found at https://pubs.aip.org/aip/pop/article-abstract/17/5/052503/920544/Sub-Alfvenic-velocity-limits-in?redirectedFrom=fulltext.

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Abstract

Magnetized plasmas in shaped fields rely on large, supersonic rotation to effect centrifugal confinement of plasma along magnetic field lines. The results of experiments on the Maryland Centrifugal Experiment (MCX) [R. F. Ellis et al, Phys. Plasmas 12, 055704 (2005)] to document velocity limits are reported. Previous results have shown a limit at the Alfvén speed, consistent with equilibrium limits from ideal magnetohydrodynamic theory. Another speed limit, previously reported as possibly related to a critical ionization phenomenon and depending only on the ion species and the shape of the confining magnetic field, is investigated here for a broad range of the applied parameters. We show that this speed limit manifests at sub-Alfvénic levels and that, as externally applied torques on the plasma are increased, the extra momentum input shows up as enhanced plasma density or lower momentum confinement time, accompanied by an increase in the neutral radiation level. Several key parameters are scanned, including the mirror ratio, the length between insulators, and the species mass. We show that this velocity limit is consistent with the species-dependent critical ionization velocity postulated by Alfvén.