Title: Nonlinear error field response in the presence of plasma rotation and real frequencies due to favorable curvature

Abstract

We present nonlinear NIMROD resistive MHD simulations of the response of a rotating plasma to an error field when the plasma has weakly damped linear tearing modes (TMs), stabilized by a pressure gradient and favorable curvature. The favorable curvature leads to the Glasser effect: the occurrence of real frequencies and stabilization with positive stability index Δ′. A cylinder with hollow pressure is used to model the toroidal favorable curvature. Linear simulations with rotation and an error field ψ̃w show that, in agreement with analytical results, the peak reconnected flux occurs for a rotation rate near the TM phase velocity. Nonlinear simulations with small ψ̃w show that the real frequency and stabilization by the favorable average curvature are masked by a nonlinear effect that occurs for very thin islands: flattening of the pressure across the island, mainly due to sound wave propagation. This flattening causes the disappearance of real frequency and destabilization of the mode, allowing it to grow to large amplitude similar to a β = 0 unstable TM. The flattening of the current for larger islands saturates the mode nonlinearly. In the post-saturation phase, the interaction of the error field with the destabilized spontaneous tearing mode, which rotates withmore » the plasma, leads to oscillations in the Maxwell torque and therefore modulations in the plasma rotation. The islands also rotate with modulated phase velocity, undergoing small-amplitude oscillations due to these modulations. We also present a quasilinear model with an unstable spontaneous TM and error fields, showing that the superposition of these fields results in similar oscillations.« less

Authors:

Akçay, Cihan ^[1]; Finn, John M. ^[1]; Cole, Andrew J. ^[2]; Brennan, Dylan P.  ^[3]

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+ Show Author Affiliations

1. Tibbar Plasma Technologies Incorporated, Los Alamos, NM (United States)
2. Columbia Univ., New York, NY (United States)
3. Princeton Univ., NJ (United States)

Publication Date:

Wed Mar 04 00:00:00 EST 2020

Research Org.:

Tibbar Plasma Technologies Incorporated, Los Alamos, NM (United States)

Sponsoring Org.:

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

Contributing Org.:

NERSC

OSTI Identifier:

1773816

Alternate Identifier(s):

OSTI ID: 1602893

Grant/Contract Number:  

SC0019016; SC0014119; SC0014005; AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 27; 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; Magnetic fields; Nonlinear systems; Doppler effect; Plasma properties and parameters; Magnetohydrodynamics; Plasma confinement; Plasma instabilities; Tokamaks; Linear stability analysis; Plasma flows