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Study Investigates Mystery of Fluid Flow in Stellar and Planetary Environments

Simulations run on Expanse supercomputer reveal patterns of instability around solar flares

Published May 17, 2023

 Credit: NASA Goddard Space Flight Center

By Kimberly Mann Bruch

In September 1859, Richard Christopher Carrington and Richard Hodgson each recorded a very intense solar flare—a sudden explosion of energy coming off the Sun. To date, the Carrington Event as it was called remains one of the most powerful solar storms on record. While the awe-inspiring auroras created by the intense geomagnetic storms were seen around the world, a solar flare of the same magnitude would wreak havoc on today’s complex technological and communications systems. Hence, the turbulence involved with such flares is often studied by scientists such as Adrian Fraser.

While a postdoctoral researcher at UC Santa Cruz, Fraser used Expanse at the San Diego Supercomputer Center (SDSC) at UC San Diego to simulate a set of fluid flows that may someday help researchers predict the frequency and intensity of a solar flare. He said that his study focused on the dynamics behind the flares and the possibility of predicting the frequency of the intense “burps” from the Sun that cause auroras.

“A geomagnetic storm like the Carrington Event could wipeout global power grids,” Fraser said. “Our study looked at a set of fluid flows that some believe impact the Sun’s behavior, and we used Expanse to simulate these flows.”

Fraser explained that the study looked specifically at continuing patterns of fluid flows sliding past one another and how this happens in exotic environments like stellar interiors or planetary atmospheres. For instance, the horizontal bands seen when looking at Jupiter are such flows—sliding past one another in a repeated pattern.

Fraser worked with UC Santa Cruz Applied Mathematics Professor Pascale Garaud and University of Colorado, Boulder Graduate Student Imogen Creswell to publish his most recent study in a paper entitled Non-ideal instabilities in sinusoidal shear flows with a streamwise magnetic field in The Journal of Fluid Mechanics.


[View full image] A snapshot from an Expanse-generated simulation that shows the vertical flow velocity at each position. The simulation began with a repeating pattern of up-flows and down-flows alongside one another, like a 90-degree rotation of the horizontal bands seen on Jupiter's surface. If that configuration were stable, the flow would have stayed like that forever. Instead, these surprising kinks eventually develop, and perturb the bands that would otherwise be perfectly straight and vertical. Credit: A. Fraser.

According to Fraser,  the study’s findings were surprising. “We thought that we would see fluid flow that was stable, like a No. 2 pencil balanced on its flat eraser,” he said. “Instead, the Expanse-generated simulation showed that the fluid flow was unstable, more like when a pencil is balanced precariously on its tip. This result perplexed us.”

Since conducting this study, Fraser has gone on to the University of Colorado, Boulder, where he plans to continue to use Expanse for his postdoctoral research and delve farther into this perplexing phenomenon.

“As a scientist, I look at the technical aspects of events like auroras and the turbulence involved—trying to better understand the fluid flow—then I convey my findings in publications so that other researchers can work toward early warning systems development,” Fraser said. “It’s also one of the reasons that we need robust infrastructure in place—should a solar flare as strong as the Carrington Event occur again.”

In addition to the turbulence affiliated with auroras, Fraser also looks at how lithium is lost from the surface of red giant branch (RGB) stars. He said that he believes that this lithium loss is caused by turbulence—similar to the kind described in his recent publication—and to simulate these types of studies he needs access to a supercomputer.

“We are probing unique kinds of turbulence that haven’t been simulated before. This is the kind of research that is the breeding ground for new types of models that have high impact wherever turbulence is found,” Fraser said. “With the help of Expanse at SDSC, we’re able to create simulations that help us get closer to solving the mystery of fluid flow.”

Fraser’s computational work used the National Science Foundation Extreme Science and Engineering Discovery Environment (allocation AST180055).