Authors

Citation

Dr. Mccarthy et al., Reduction in transport by the parallel velocity shear instability due to reversed magnetic shear, PHYS PLASMA, 8(8), 2001, pp. 3645-3651

Citations number

11

Language

INGLESE

art.tipo

Article

Categorie Soggetti

Physics

Journal title

PHYSICS OF PLASMAS

ISSN journal

1070-664X
â†’ ACNP

Volume

8

Issue

8

Year of publication

2001

Pages

3645 - 3651

Database

ISI

SICI code

1070-664X(200108)8:8<3645:RITBTP>2.0.ZU;2-Z

Abstract

A nonlocal theory of the electrostatic parallel velocity shear instability
in a three-dimensional slab with a uniformly sheared magnetic field has bee
n developed. It is shown that in the limit of a weak parallel velocity grad
ient, the linear growth rate can be increased depending upon the direction
of the magnetic shear ((s) over cap) with respect to the radial curvature o
f the parallel velocity profile (d(2)v(parallel to)/dx(2)). When these para
meters have the same sign, the growth rate can actually be stronger than in
the limit of no magnetic shear. In this limit of increased instability, th
e eigenmode is broadened, thus producing enhanced transport. This effect sh
ould be observable when the scale length of the curvature is of order simil
ar to rootL(s)rho (s). For strong parallel velocity gradients that are more
typical of flows in tokamaks, the effect of the varying Doppler shift beco
mes more prominent on the stability of the mode, the net result being that
the sensitivity of the growth rates on the sign of the magnetic shear becom
es insignificant. This effect, however, is effectively offset when a finite
density gradient is included. When the density scale length is of order th
e scale length of v(parallel to), the growth rate is moderately reduced, bu
t becomes dependent again upon the sign of the magnetic shear. (C) 2001 Ame
rican Institute of Physics.