Abstract Details
Abstracts
Author: Zhisong Qu
Requested Type: Poster
Submitted: 2019-02-07 01:52:06
Co-authors: R.L. Dewar, S.R. Hudson, M.J. Hole
Contact Info:
the Australian National University
the Australian National Univer
Canberra, ACT 2601
Australia
Abstract Text:
The Multiregion Relaxed MHD[1] was successful in the construction of equilibria in 3D configurations, bridging the gap between Taylor relaxation, which allows relaxation but over coarse-grained the problem, and ideal MHD, which includes no relaxation at all but infinite constraints. In MRxMHD, we consider the case of a toroidal plasma laminated into multiple nested annular toroidal relaxation regions, separated by interfaces supporting current sheets. Unlike ideal MHD, Taylor relaxation allows reconnection at resonant surfaces to occur within these regions, leading to saturated islands and chaotic magnetic fields.
It has been postulated[2] that plasma flow may stabilize such current sheets even if they occur on surfaces that resonate with boundary perturbations in 3D geometries such as stellarators, or tokamaks with resonant magnetic perturbation (RMP) coils. This motivates the extension of the 3D-MRxMHD-based equilibrium code SPEC[3] to allow plasma flow with reasonably general flow profiles.
In this work, we will discuss MRxMHD with flow. By minimizing total energy with constant mass, entropy and fluid helicity, one can reach a Taylor-like relaxation model[4] for fluids. On the other hand, Finn etal. [5] and Dennis etal.[6] have proposed setting the cross flow helicity as a constraint, leading to a non-relax flow but consistent with ideal MHD in limit of infinite interfaces. We will study the implication of different constraints and give examples of the corresponding flow and its impact.
[1] M. Hole, S. Hudson, and R. Dewar, Nucl. Fusion 47, 746 (2007).
[2] R.L. Dewar, S.R. Hudson et al., Phys. Plasmas, 24, 042507-1–18, (2017).
[3] S.R. Hudson, R.L. Dewar et al., Phys. Plasmas 19, 112502-1–18, (2012).
[4] N. Sato and R.L. Dewar, https://arxiv.org/pdf/1708.06193.pdf.
[5] J.M. Finn and T.M. Antonsen, Jr., Phys. Fluids 26, 3540 (1983).
[6] G.R. Dennis, S.R. Hudson, R.L. Dewar and M.J. Hole, Phys. Plasmas 19, 0425011–9, (2014).
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