RAPID: Potential Vorticity Mixing Experiments on COMPASS Plasma Device

University Of California-San Diego, La Jolla CA

Investigators

Abstract

This award will support an experimental plasma-based study of how large-scale flows may emerge from small-scale turbulence in rotating systems. The behavior of fluid-like media in rotating stars and gas giant planets, in the oceans and molten cores of rotating Earth-like planets, and in plasmas with strong magnetic fields is profoundly affected by the forces associated with the overall rotation on the medium itself. These forces lead to the emergence of well ordered, slowly varying sheared flows. Theory predicts that all such systems share the same underlying origin of the sheared flows via a quantity known as the potential vorticity. In a rotating fluid, for example in geophysical, planetary and stellar systems, the potential vorticity is given by a combination of the local fluid vorticity and the planetary rotation itself. The experimental study supported by this award will make the first-ever attempt to directly test the role that potential vorticity plays in the formation of sheared flows in turbulent magnetized plasmas and will have broader implications for future development of fusion energy sources. The experiment will be performed on the COMPASS plasma device in the Czech Republic, and the subsequent data analysis will be carried out by upper-division undergraduate students. This project will provide an experimental test of the theoretical prediction that turbulence-generated shear flows appear in magnetized toroidal plasmas due to the effects of a strong Lorentz force, and as such follow similar underlying nonlinear dynamics to that responsible for shear flow formation found in the atmospheres of planets and stars due to the effects of the Coriolis force. Should this experiment demonstrate that this is the case, it would provide a strong link between these two seemingly disparate physical systems. Should the result show that the prediction is in fact incorrect, it would then force a fundamental rethinking of the theory. In either case, the outcome will impact our understanding of self-organization processes in turbulent fluid and plasma systems. This award is supported by the Division of Physics with additional support from the Office of Multidisciplinary Activities and the Office of International Science and Engineering. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.