Nonlinear coupling of tearing fluctuations in the Madison Symmetric Torus
- Wisconsin Univ., Madison, WI (United States)
- Fermi National Accelerator Lab., Batavia, IL (United States)
- Oak Ridge National Lab., TN (United States)
Three-wave, nonlinear, tearing mode coupling has been measured in the Madison Symmetric Torus (MST) reversed-field pinch (RFP) [Fusion Technol. 19, 131 (1991)] using bispectral analysis of edge magnetic fluctuations resolved in ``k-space. The strength of nonlinear three-wave interactions satisfying the sum rules m{sub 1} + m{sub 2} = m{sub 3} and n{sub 1} + n{sub 2} = n{sub 3} is measured by the bicoherency. In the RFP, m=l, n{approximately}2R/a (6 for MST) internally resonant modes are linearly unstable and grow to large amplitude. Large values of bicoherency occur for two m=l modes coupled to an m=2 mode and the coupling of intermediate toroidal modes, e.g., n=6 and 7 coupled to n=13. These experimental bispectral features agree with predicted bispectral features derived from MHD computation. However, in the experiment, enhanced coupling occurs in the ``crash`` phase of a sawtooth oscillation concomitant with a broadened mode spectrum suggesting the onset of a nonlinear cascade.
- Research Organization:
- Wisconsin Univ., Madison, WI (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-85ER53198
- OSTI ID:
- 10139146
- Report Number(s):
- DOE/ER/53198-211; CONF-921103-9; ON: DE93010131
- Resource Relation:
- Conference: Meeting of the Division of Plasma Physics of the American Physical Society,Seattle, WA (United States),16-20 Nov 1992; Other Information: PBD: Nov 1992
- Country of Publication:
- United States
- Language:
- English
Similar Records
Nonlinear coupling of tearing fluctuations in the Madison Symmetric Torus
Measurement of magnetic turbulence structure and nonlinear mode coupling of tearing fluctuations in the Madison Symmetric Torus reversed field pinch edge