The “turbulent dynamo” phenomenon could help explain how small magnetic fields built momentum, eventually becoming the massive magnetic fields that pervade the cosmos. Little is known about the phenomenon, however – and researchers from the University of Rochester and the University of Oxford are working to change that with the help of supercomputers at Argonne National Laboratory.
The team used the supercomputers to prepare for an experiment at the University of Rochester’s Omega Laser Facility, which hosts a 70-meter-long laser system of 60 laser beams that is capable of producing enormously powerful beams for very brief periods of time (billionths of a second). Operating this laser system, of course, is expensive. To establish the parameters for the real-world experiments, the team made use of Argonne’s supercomputing resources. Those resources are currently dominated by the 6.9-Linpack petaflops Theta system, but will soon be joined by the Aurora exascale system and, even sooner, Aurora’s 44-peak petaflops testbed, called Polaris.
The researchers simulated the experiment using the FLASH code from the University of Chicago’s Flash Center Code Group, which is used to model plasma physics and astrophysics. The code was appropriate for the study of turbulent dynamo, which involves plasma-dense regions of space.
With parameters in-hand from the supercomputer simulations, the team was able to successfully reproduce key conditions in a real-world laboratory experiment.
“These laser-driven plasma experiments enabled us to reproduce the turbulent dynamo mechanism and, for the first time in the laboratory, access the viscosity-dominated regime that is relevant to most plasmas in the universe,” said Petros Tzeferacos, an astrophysicist at the University of Rochester and co-author of the paper, in an interview with Argonne’s Nils Heinonen. “This was also the first instance in which we’ve been able to successfully record time-resolved measurements of the properties of the mechanism, including the growth rate of the magnetic field, which could previously only be studied via simulation. … Our team’s efforts answer key astrophysics questions and establish laboratory experiments as a component in the study of turbulent dynamo.”
This study is, itself, a followup to a 2018 study that proved the existence of turbulent dynamo – a study that also made use of Argonne supercomputers. The new study confirmed that the effects of turbulent dynamo are able to quickly produce large magnetic fields.
To learn more about this research, read the coverage from Argonne’s Nils Heinonen here.
About the research
The research discussed in this article was published as “Time-resolved turbulent dynamo in a laser plasma” in the March 2021 issue of PNAS. It can be accessed here.