Experimental Characterization of Three-Wave Coupling in Dipole Plasma Turbulence
Abstract
Plasmas confined by a strong dipole field exhibit interchange turbulence, which previous experiments have shown respond locally to active feedback [1]. On the Collisionless Terrella Experiment (CTX), this turbulence is characterized by low frequency, low order, quasi-coherent modes with time-varying and intermittent spectral dynamics. We apply bicoherence analysis [2] using both short time fourier transforms and wavelets as basis functions to study nonlinear three-wave coupling and the resulting energy transfer between scales in the naturally occurring turbulence, as well as during active feedback and driven wave scenarios. The drive/feedback system can both amplify and suppress local turbulent fluctuations. During feedback we observe enhancements to the time-averaged bicoherence, while on shorter timescales the bicoherence changes rapidly with variations in fluctuation intensity.
[1] Roberts, Mauel, and Worstell, Phys Plasmas (2015). [2] Grierson, Worstell, and Mauel, Phys Plasmas (2009). Supported by NSF-DOE Partnership for Plasma Science Grants DOE-DE-FG02-00ER54585 and NSF-PHY-1201896.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH13E3457A
- Keywords:
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- 2134 Interplanetary magnetic fields;
- INTERPLANETARY PHYSICS;
- 2159 Plasma waves and turbulence;
- INTERPLANETARY PHYSICS;
- 2164 Solar wind plasma;
- INTERPLANETARY PHYSICS;
- 4415 Cascades;
- NONLINEAR GEOPHYSICS