Title: Two-fluid and finite Larmor radius effects on helicity evolution in a plasma pinch

Abstract

In this, the evolution of magnetic energy, helicity, and hybrid helicity during nonlinear relaxation of a driven-damped plasma pinch is compared in visco-resistive magnetohydrodynamics and two-fluid models with and without the ion gyroviscous stress tensor. Magnetic energy and helicity are supplied via a boundary electric field which initially balances the resistive dissipation, and the plasma undergoes multiple relaxation events during the nonlinear evolution. The magnetic helicity is well conserved relative to the magnetic energy over each event, which is short compared with the global resistive diffusion time. The magnetic energy decreases by roughly 1.5% of its initial value over a relaxation event, while the magnetic helicity changes by at most 0.2% of the initial value. The hybrid helicity is dominated by magnetic helicity in low-β pinch conditions and is also well conserved. Differences of less than 1% between magnetic helicity and hybrid helicity are observed with two-fluid modeling and result from cross helicity evolution. The cross helicity is found to change appreciably due to the first-order finite Larmor radius effects which have not been included in contemporary relaxation theories. The plasma current evolves towards the flat parallel current state predicted by Taylor relaxation theory but does not achieve it. Plasmamore » flow develops significant structure for two-fluid models, and the flow perpendicular to the magnetic field is much more substantial than the flow along it.« less

Authors:

Sauppe, J. P. ^[1]; Sovinec, C. R. ^[2]

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+ Show Author Affiliations

1. Univ. of Wisconsin, Madison, WI (United States). Center for Plasma Theory and Computation and Dept. of Physics
2. Univ. of Wisconsin, Madison, WI (United States). Center for Plasma Theory and Dept. of Engineering-Physics

Publication Date:

Thu Mar 03 00:00:00 EST 2016

Research Org.:

Univ. of Wisconsin, Madison, WI (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; National Science Foundation (NSF)

OSTI Identifier:

1461731

Alternate Identifier(s):

OSTI ID: 1240201

Grant/Contract Number:  

FG02-06ER54850; PHY-0821899; AC02-05CH1123

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 23; Journal Issue: 3; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; diffusion; plasma flows; electrical resistivity; magnetohydrodynamics; viscosity; boundary value problems; electric currents; parallel processing; electric fields; magnetic fields