ROLE OF FLOW SHEAR AND FLOW CURVATURE IN THE SUPPRESSION OF LOW-FREQUENCY FLUCTUATIONS

The crucial question of whether it is the shear [V(r)'] or the curvatu re [V(r)''] in the flow profile [V(r)], which plays the dominant role in suppressing the low-frequency (omega < omega(i), where omega(i) is the ion gyrofrequency) fluctuations is investigated. The role of flow curvature is found to have a robust effect on the fluctuations. For a positive value in the flow curvature, fluctuations are suppressed, whe reas a negative flow curvature excites fluctuations. Flow shear, on th e other hand, plays an insignificant role in this matter. These experi mental findings are in complete agreement with the theoretical predict ions. (C) 1998 American Institute of Physics. [S1070-664X(98)02007-2]