ParameterSpace Survey of Linear Gmode and Interchange in Extended Magnetohydrodynamics
Abstract
The extended magnetohydrodynamic stability of interchange modes is studied in two configurations. In slab geometry, a local dispersion relation for the gravitational interchange mode (gmode) with three different extensions of the MHD model [P. Zhu, et al., Phys. Rev. Lett. 101, 085005 (2008)] is analyzed. Our results delineate where drifts stablize the gmode with gyroviscosity alone and with a twofluid Ohm’s law alone. Including the twofluid Ohm’s law produces an ion drift wave that interacts with the gmode. This interaction then gives rise to a second instability at finite k _{y}. A second instability is also observed in numerical extended MHD computations of linear interchange in cylindrical screwpinch equilibria, the second configuration. Particularly with incomplete models, this mode limits the regions of stability for physically realistic conditions. But, applying a consistent twotemperature extended MHD model that includes the diamagnetic heat flux density ($$\vec{q}$$ _{*}) makes the onset of the second mode occur at larger Hall parameter. For conditions relevant to the SSPX experiment [E.B. Hooper, Plasma Phys. Controlled Fusion 54, 113001 (2012)], significant stabilization is observed for Suydam parameters as large as unity (D _{s}≲1).
 Authors:
 Univ. of Wisconsin, Madison, WI (United States). Dept. of Engineering Physics
 Publication Date:
 Research Org.:
 Univ. of Wisconsin, Madison, WI (United States)
 Sponsoring Org.:
 USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC24)
 OSTI Identifier:
 1390175
 Alternate Identifier(s):
 OSTI ID: 1395917
 Report Number(s):
 UWCPTC 175
Journal ID: ISSN 1070664X
 Grant/Contract Number:
 FG0206ER54850; FC0205ER54813; FC0208ER54975
 Resource Type:
 Journal Article: Accepted Manuscript
 Journal Name:
 Physics of Plasmas
 Additional Journal Information:
 Journal Volume: 24; Journal Issue: 10; Journal ID: ISSN 1070664X
 Publisher:
 American Institute of Physics (AIP)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; mathematical foundations: fluid and multifluid theory; instabilities: hydromagnetic; computer simulation: MHD
Citation Formats
Howell, E. C., and Sovinec, C. R. ParameterSpace Survey of Linear Gmode and Interchange in Extended Magnetohydrodynamics. United States: N. p., 2017.
Web. doi:10.1063/1.4993440.
Howell, E. C., & Sovinec, C. R. ParameterSpace Survey of Linear Gmode and Interchange in Extended Magnetohydrodynamics. United States. doi:10.1063/1.4993440.
Howell, E. C., and Sovinec, C. R. 2017.
"ParameterSpace Survey of Linear Gmode and Interchange in Extended Magnetohydrodynamics". United States.
doi:10.1063/1.4993440.
@article{osti_1390175,
title = {ParameterSpace Survey of Linear Gmode and Interchange in Extended Magnetohydrodynamics},
author = {Howell, E. C. and Sovinec, C. R.},
abstractNote = {The extended magnetohydrodynamic stability of interchange modes is studied in two configurations. In slab geometry, a local dispersion relation for the gravitational interchange mode (gmode) with three different extensions of the MHD model [P. Zhu, et al., Phys. Rev. Lett. 101, 085005 (2008)] is analyzed. Our results delineate where drifts stablize the gmode with gyroviscosity alone and with a twofluid Ohm’s law alone. Including the twofluid Ohm’s law produces an ion drift wave that interacts with the gmode. This interaction then gives rise to a second instability at finite ky. A second instability is also observed in numerical extended MHD computations of linear interchange in cylindrical screwpinch equilibria, the second configuration. Particularly with incomplete models, this mode limits the regions of stability for physically realistic conditions. But, applying a consistent twotemperature extended MHD model that includes the diamagnetic heat flux density ($\vec{q}$*) makes the onset of the second mode occur at larger Hall parameter. For conditions relevant to the SSPX experiment [E.B. Hooper, Plasma Phys. Controlled Fusion 54, 113001 (2012)], significant stabilization is observed for Suydam parameters as large as unity (Ds≲1).},
doi = {10.1063/1.4993440},
journal = {Physics of Plasmas},
number = 10,
volume = 24,
place = {United States},
year = 2017,
month = 9
}

Drift wave versus interchange turbulence in tokamak geometry: Linear versus nonlinear mode structure
The competition between drift wave and interchange physics in general EcrossB drift turbulence is studied with computations in threedimensional tokamak flux tube geometry. For a given set of background scales, the parameter space can be covered by the plasma {beta} and drift wave collisionality. At large enough plasma {beta} the turbulence breaks out into ideal ballooning modes and saturates only by depleting the free energy in the background pressure gradient. At high collisionality it finds a more gradual transition to resistive ballooning. At moderate {beta} and collisionality it retains drift wave character, qualitatively identical to simple twodimensional slab models. Themore » 
Comparison of kinetic and extended magnetohydrodynamics computational models for the linear ion temperature gradient instability in slab geometry
We perform linear stability studies of the ion temperature gradient (ITG) instability in unsheared slab geometry using kinetic and extended magnetohydrodynamics (MHD) models, in the regime k{sub ∥}/k{sub ⊥}≪1. The ITG is a parallel (to B) sound wave that may be destabilized by finite ion Larmor radius (FLR) effects in the presence of a gradient in the equilibrium ion temperature. The ITG is stable in both ideal and resistive MHD; for a given temperature scale length L{sub Ti0}, instability requires that either k{sub ⊥}ρ{sub i} or ρ{sub i}/L{sub Ti0} be sufficiently large. Kinetic models capture FLR effects to all ordersmore » 
Parameter spaces for linear and nonlinear whistlermode waves
We examine the growth of magnetospheric whistlermode waves which comprises a linear growth phase followed by a nonlinear growth phase. We construct timeprofiles for the wave amplitude that smoothly match at the transition between linear and nonlinear wave growth. This matching procedure can only take place over a limited “matching region” in (N{sub h}/N{sub 0},A{sub T})space, where A{sub T} is the electron thermal anisotropy, N{sub h} is the hot (energetic) electron number density, and N{sub 0} is the cold (background) electron number density. We construct this matching region and determine how the matching wave amplitude varies throughout the region. Further,more »