San Diego, Calif., May 21, 2019 -- The first image of a supermassive black hole – the image that took the internet by storm in April 2019 – actually depicts a plasma rapidly swirling around the black hole. Closer to home, we all experience the effects of the jet stream when the polar vortex brings severe winter weather deep into mid-latitude regions. Despite the recent attention and familiarity of these large-scale organized flows of plasmas and fluids, there is still a lot about how such flows develop - particularly in magnetized plasmas - that we don’t understand.
Caption: The first direct visual evidence of a supermassive black hole and its shadow. Image credit: NSF
A new grant from the National Science Foundation is providing a University of California San Diego team with a unique opportunity to study – experimentally – how large-scale flows emerge and organize themselves from small-scale random turbulent fluctuations in magnetized laboratory plasmas.
The work could also bring researchers closer to developing fusion energy devices that hold the tantalizing promise of massive amounts of clean energy.
Caption top image: NASA Cassini imaging of similar flow in Saturn's Polar Region, image credit: NASA/JPL-Caltech/Space Science Institute /
What’s the connection between the plasma swirling around supermassive black holes, the jet stream, and fusion energy devices? Theorists have predicted that a common underlying mechanism may explain: 1) How turbulent plasma flows organize around black holes, 2) How self-organized flows can develop in magnetized fusion plasmas, and even 3) How flows self-organize in oceans and molten cores of rotating Earth-like planets.
“This grant offers my research team an opportunity to test the theoretical prediction that the same processes at work in the Earth’s jet stream govern the self-organization of flow development in magnetized plasmas,” said UC San Diego mechanical and aerospace engineering professor George Tynan, the PI on the project.
The grant sets up a collaborative research program connecting UC San Diego to researchers working on the COMPASS tokamak facility at the Institute of Plasma Physics of the Czech Academy of Sciences in Prague.
“Together, we’ll have a unique opportunity to perform a series of direct experimental tests of the self-organization processes in this turbulent plasma system,” said Tynan.
This approximately $200k NSF RAPID (Rapid Response Research) award is supported by the NSF Division of Physics with additional support from the Office of International Science and Engineering.
“With this grant, George Tynan’s team will have the opportunity to study questions that unify otherwise disparate scientific disciplines. The COMPASS plasma facility has unique diagnostic capabilities which make it ideal for this project, and it is only fitting that the project will bring together scientists separated by nine time zones,” said Vyasheslav (Slava) Lukin, Program Director for Plasma Physics at the National Science Foundation.
The collaboration opportunity between U.S. researchers and researchers at the COMPASS tokamak facility arose while Lukin was in the Czech Republic participating in the Embassy Science Fellows Program which is run by the U.S. Department of State.
The Embassy Science Fellows program, according to the U.S. Department of State, leverages the expertise of U.S. government scientists to build relationships and partnerships that advance American foreign policy and scientific priorities, further our understanding of worldwide science trends, promote U.S. scientific norms, and advance American foreign policy interests.
The new funding from NSF will support an experimental plasma-based study of how large-scale flows may emerge from small-scale stochastic turbulence.
|Image caption: The flow field of a similar shear flow in the CSDX magnetized laboratory plasma device at the University of California San Diego, taken from a paper from professor George Tynan’s research group: C. Brandt et al, Physics of Plasmas 23, 042304 (2016). The flow field forms a nearly impermeable barrier at a radius of about 2-3 cm, similar to the barrier between the polar regions and the mid-latitude regions formed by the jet stream. The COMPASS experiment will measure the potential vorticity in a plasma and test whether or not it exhibits similar PV dynamics found in the atmosphere of rotating planets. Such barrier formation in a fusion device makes it easier to "insulate" the hot (100 Million degree K) core plasma from the cooler (<1 Million degree K) outer regions and thus maintain the high temperature needed for fusion to occur|
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 rotation of the planet or star, or the magnetic field in a plasma system.
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. Likewise, theory suggests that a similar quantity operates in a magnetized plasma.
“Thanks to this NSF funding, we are going to make the first-ever attempt to directly test the role that potential vorticity plays in the formation of sheared flows found in the edge of confined magnetized plasmas,” said Tynan. “Such flow formation in a fusion device makes it easier to "insulate" the hot (100 Million degree K) core plasma from the cooler (<1 Million degree K) outer regions and thus maintain the high temperature needed for fusion to occur. As part of this project, upper-division UC San Diego undergraduate students will be directly involved in the analysis of the data emerging from this experiment.”
In particular, the 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.
NSF award info: Potential Vorticity Mixing Experiments on COMPASS Plasma Device