摘要:

Nonlocal effects due to magnetic shear and finite current channel width on the convective characteristics of the current‐driven ion‐cyclotron instability have been investigated. When the magnetic shear length (Ls) is smaller than the current channel width (Lc), the group velocity parallel to the external magnetic field at the origin (Vgz) vanishes, and there is a reduction in the group velocity perpendicular to the external magnetic field (Vgy). ForLc∼10−2Lsthe values ofVgzandVgyas given by local theory are recovered. WhenLc≲&rgr;i, where &rgr;iis the mean ion Larmor radius, bothVgzandVgychange sign, indicating a reversal of the direction of propagation.

ISSN:0031-9171    

DOI:10.1063/1.864860

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The evolution of a single helicity tearing mode is analyzed by kinetic theory, including modification of the electron orbits by the islands themselves. Using flux coordinates appropriate to island geometry, analytic solutions for the time‐dependent island width are obtained. These describe evolution from linear growth to nonlinear saturation in the collisionless limit, and transition from such saturation to slow Rutherford‐type growth for increasing finite collisionality. Previous work is thus unified and generalized.

ISSN:0031-9171    

DOI:10.1063/1.864861

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

It is shown that the magnetic‐field gradient in a shock wave can result in a stabilizing effect on the electron‐cyclotron‐drift instability and consequently tends to reduce the growth rate significantly. The present discussion generalizes the earlier work of Sanderson and Priest who also considered similar problems.

ISSN:0031-9171    

DOI:10.1063/1.864862

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The response of a finite conductivity plasma to resonant magnetic perturbations is studied. The equations, which are derived for the time development of magnetic islands, help one to interpret the singular currents which occur under the assumption of perfect plasma conductivity. The relation to the Rutherford regime of resistive instabilities is given.

ISSN:0031-9171    

DOI:10.1063/1.864863

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A cylindrical axisymmetric tearing mode model for solar flares is investigated numerically. Large magnetic energy release only occurs when there are at least two mode rational surfaces in the current‐carrying plasma.

ISSN:0031-9171    

DOI:10.1063/1.864864

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The stability of the electron drift wave is investigated in the presence ofE×Bplasma rotation typical of the central cell plasma in tandem mirrors. It is shown that a rotationally driven drift wave may occur at low azimuthal mode numbers. Conditions for rotational instabilities are derived. Quasilinear formulas are given for the anomalous transport associated with the unstable fluctuations.

ISSN:0031-9171    

DOI:10.1063/1.864865

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A self‐consistent theory is presented for particle flows in the flux surface, radial particle fluxes, and the radial electric field in a tokamak. The effects of beam‐impurity momentum exchange, radial transfer of toroidal momentum, and the poloidal variation in density and potential which ensue whenv&fgr;&bartil;vthare treated—the interaction among these effects is nonlinear. Model problem predictions based on the theory indicate enhanced inward impurity transport with strong counterinjection and outward impurity transport with strong coinjection of neutral beams.

ISSN:0031-9171    

DOI:10.1063/1.864866

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The portion &Fgr;1of the ambipolar potential &Fgr; which produces an electric field in the flux surfaces of a stellarator is self‐consistently calculated, and its effect on stellarator transport at low collisionality is considered. The effect is small in a parameter &dgr;h, which is proportional to the square root of the ripple amplitude, &egr;h. However, since &dgr;hcan be an appreciable fraction of 1 for realistic parameters, the effect of &Fgr;1on transport can also be appreciable. Whether the effect is harmful or beneficial to confinement depends on the degree of pressure anisotropy and on the sign ofp⊥−p∥.

ISSN:0031-9171    

DOI:10.1063/1.864867

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A class of low‐&bgr; stellarator magnetohydrodynamic (MHD) equilibria with &bgr;∼(a/R0)2is introduced, and the corresponding toroidal shift is calculated. It is shown that an apparent paradox exists with regard to the problem of position control in that a vertical field is capable of shifting vacuum flux surfaces, but produces no net body force on a current‐free stellarator. This paradox is resolved by an analysis of the transient response of the plasma and demonstrates how the vertical field can be used as a means of position control.

ISSN:0031-9171    

DOI:10.1063/1.864833

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

An average method based on a vacuum flux coordinate system is presented. This average method permits the study of helical axis stellarators with toroidally dominated shifts. An ordering is introduced, and to lowest order the toroidally averaged equilibrium equations are reduced to a Grad–Shafranov equation. Also, to lowest order, a Poisson‐type equation is obtained for the toroidally varying corrections to the equilibrium. By including these corrections, systems that are toroidally dominated, but with significant helical distortion to the equilibrium, may be studied. Numerical solutions of the average method equations are shown to agree well with three‐dimensional calculations.

ISSN:0031-9171    

DOI:10.1063/1.864834

出版商:AIP    

年代:1984

数据来源: AIP