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Driven, dissipative, energy-conserving magnetohydrodynamic equilibria. Part 2. The screw pinch

Published online by Cambridge University Press:  13 March 2009

Michael L. Goodman
Affiliation:
Universities Space Research Association, and Code 695, Planetary Magnetospheres Branch, Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, U.S.A.

Abstract

A cylindrically symmetric, electrically driven, dissipative, energy-conserving magnetohydrodynamic equilibrium model is considered. The high-magneticfield Braginskii ion thermal conductivity perpendicular to the local magnetic field and the complete electron resistivity tensor are included in an energy equation and in Ohm's law. The expressions for the resistivity tensor and thermal conductivity depend on number density, temperature, and the poloidal and axial (z-component) magnetic field, which are functions of radius that are obtained as part of the equilibrium solution. The model has plasma-confining solutions, by which is meant solutions characterized by the separation of the plasma into two concentric regions separated by a transition region that is an internal boundary layer. The inner region is the region of confined plasma, and the outer region is the region of unconfined plasma. The inner region has average values of temperature, pressure, and axial and poloidal current densities that are orders of magnitude larger than in the outer region. The temperature, axial current density and pressure gradient vary rapidly by orders of magnitude in the transition region. The number density, thermal conductivity and Dreicer electric field have a global minimum in the transition region, while the Hall resistivity, Alfvén speed, normalized charge separation, Debye length, (ωλ)ion and the radial electric field have global maxima in the transition region. As a result of the Hall and electron-pressure-gradient effects, the transition region is an electric dipole layer in which the normalized charge separation is localized and in which the radial electric field can be large. The model has an intrinsic value of β, about 13·3%, which must be exceeded in order that a plasma-confining solution exist. The model has an intrinsic length scale that, for plasma-confining solutions, is a measure of the thickness of the boundary-layer transition region. If appropriate boundary conditions are given at R = 0 then the equilibrium is uniquely determined. If appropriate boundary conditions are given at any outer boundary R = a then the equilibrium exhibits a bifurcation into two states, one of which exhibits plasma confinement and carries a larger axial current than the other, which is almost homogeneous and cannot confine a plasma. Exact expressions for the two values of the axial current in the bifurcation are derived. If the boundary conditions are given at R = a then a solution exists if and only if the constant driving electric field exceeds a critical value. An exact expression for this critical electric field is derived. It is conjectured that the bifurcation is associated with an electric-field-driven transition in a real plasma, between states with different rotation rates, energy dissipation rates and confinement properties. Such a transition may serve as a relatively simple example of the L—H mode transition observed in tokamaks.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1993

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References

Balescu, R. 1988 a Transport Processes in Plasmas, vol. 1. North-Holland.Google Scholar
Balescu, R. 1988 b Transport Processes in Plasmas, vol. 2. North-Holland.Google Scholar
Book, D. L. 1990 NRL Plasma Formulary, p. 37. Naval Research Laboratory, Washington, D.C.CrossRefGoogle Scholar
Braginskii, S. I. 1965 Reviews of Plasma Physics, vol. 1 (ed. Leontovich, M. A.), p. 205. Consultants Bureau.Google Scholar
De Kluiver, N., Perepelkin, N. F. & Hirose, A. 1991 Phys. Rep. 199, 281.CrossRefGoogle Scholar
Dreicer, H. 1959 Phys. Rev.. 115, 238.CrossRefGoogle Scholar
Dreicer, H. 1960 Phys. Rev.. 117, 329.CrossRefGoogle Scholar
Freidberg, J. P. 1982 Rev. Mod. Phys. 54, 801.CrossRefGoogle Scholar
Galeev, A. A. & Sagdeev, R. Z. 1965 Reviews of Plasma Physics, vol. 1 (ed. Leontovich, M. A.), p. 205. Consultants Bureau.Google Scholar
Goodman, M. L. 1992 J. Plasma Phys. 48, 177207.CrossRefGoogle Scholar
Hinton, F. L. & Hazeltine, R. D.. 1976 Rev. Mod. Phys. 48, 239.CrossRefGoogle Scholar
Hirshman, S. P. & Sigmar, D. J. 1981 Nucl. Fusion. 21, 1079.CrossRefGoogle Scholar
Liewer, P. C. 1985 Nucl. Fusion. 25, 543.CrossRefGoogle Scholar
Milhalas, D. & Mthalas, B. W. 1984 Foundations of Radiation Hydrodynamics, p. 49. Oxford Univesity Press.Google Scholar
Parail, V. V. & Pogutse, O. P. 1986 Reviews of Plasma Physics, vol. 11 (ed. Lcontovich, M. A.), p. 1. Consultants Bureau.Google Scholar
Store, J. & Bulirsch, R. 1980 Introduction to Numerical Analysis, chap. 7. Springer.CrossRefGoogle Scholar
Taylor, R. J. et al. 1989 Phys. Rev. Lett. 63, 2365.CrossRefGoogle Scholar