# Bulletin of the American Physical Society

# 56th Annual Meeting of the APS Division of Plasma Physics

## Volume 59, Number 15

## Monday–Friday, October 27–31, 2014; New Orleans, Louisiana

### Session BP8: Poster Session I: MHD, Energetic Particles, Predictive Modeling, Plasma Surface Interactions; Diagnostic Measurements & Analysis; Non-Neutral, Anti-Matter & Strongly Coupled Plasmas; Plasma Technology

Monday, October 27, 2014

Room: Preservation Hall

Abstract ID: BAPS.2014.DPP.BP8.25

### Abstract: BP8.00025 : Study of extended MHD effects on interchange modes in spheromak equilibria*

Preview Abstract Abstract

#### Authors:

E.C. Howell

(University of Wisconsin-Madison)

C.R. Sovinec

(University of Wisconsin-Madison)

A study of extended MHD effects on linear interchange modes is performed using the NIMROD code [Sovinec \& King JCP 2010]. A linear cylindrical equilibrium model is adapted from [Jardin NF 1982] to allow finite toroidal current at the edge. These equilibria are representative of SSPX discharges where currents are driven on the open field to keep the safety factor above $\frac{1}{2}$ across the profile [McLean et al POP 2006]. These spheromaks have weak magnetic shear, and interchange stability is an important consideration. The Suydam parameter, $D$, is scaled to study resistive and ideal interchange modes. The calculated MHD growth rate increases with $D$. The resistive interchange scaling $\gamma \sim \eta ^{1/3}$ is observed for $D < \frac{1}{4}$. Calculations using the full extended MHD model are performed for a range of hall parameters $\Lambda$. This model includes gyro-viscosity, the hall term, equilibrium diamagnetic flows, and the cross-field diamagnetic heat flux. Two fluid effects in the full model are always destabilizing at large $\Lambda$. However, some cases exhibit a range of $\Lambda$ where the growth rate for the full model is reduced relative to the MHD growth rate.

*Work supported by US DOE.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.DPP.BP8.25

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