The universe is filled with magnetic fields. Understanding how magnetic fields are generated and expanded in plasmas is essential for studying how large structures in the universe were formed and how energy is distributed throughout in cosmos.
An international collaboration, co-led by researchers at the University of Rochester, the University of Oxford, and the University of Chicago, conducted experiments captured for the first time in a laboratory setting the time history of magnetic field growth with the tempo dynamo, a physical device thought to be responsible for generating and maintaining astrophysical magnetic fields. The experiments were able to find conditions relevant to most plasmas in the universe and measured the extent to which the turbulent dynamo amplifies magnetic fields, a building that previously only came from prediction. theoretical and numerical symbols. The rapid expansion they discovered goes beyond theoretical expectation and may help explain the origin of the large galaxies seen today in galaxy assemblages. Their results were published on March 8 in the Proceedings of the National Academy of Sciences.
The researchers – part of the Turbulent Dynamo (TDYNO) team – conducted their experimental research at the Omega Laser Facility at the University of Rochester Laboratory for Laser Energy (LLE), where they had previously shown experimentally that the equipment turbulent dynamo there. That achievement won the 2019 John Dawson Award for Excellence in Plasma Physics Research from the American Corporate Association.
In their most recent experiments at the Omega Laser Facility, the researchers used a laser carrier with a total power equivalent to 10,000 nuclear reactors. They were able to perform conditions relevant to the hot, diffuse plasma of the intracluster medium in which the turbulent dynamo apparatus is thought to function. The team then measured as a time function the magnetic field extension obtained by this method.
“Understanding how and to what extent magnetic fields are expanded at macroscopic blades in astrophysical disturbances is crucial for defining the magnetic fields seen in galaxy assemblages, the largest structures in the Universe, “says Archie Bott, a postdoctoral research researcher in Princeton’s Department of Astrophysical Sciences and lead author of the study.” While numerical models and theory predict rapid turbulent dynamo expansion at scales In contrast to turbulent movements, it has been uncertain whether the equipment works fast enough to account for dynamically important areas on the largest scales. “
At the heart of the astrophysical dynamo machine is temptation. Primordial magnetic fields are generated with forces that are much smaller than those seen today in galaxy assemblages. Stochastic plasma movements, however, can lift these weak “seed” fields and increase their strengths to much greater values through stretching, twisting and folding the field. The rate at which this expansion occurs, the “growth rate,” differs for the different spatial scales of the turbulent plasma movements: theory and simulations predict that the growth rate is large. at the smallest blades but much smaller at length blades compared to those of the most turbulent movements. TDYNO experiments proved that this may not be true: turbulent dynamo – when operating in rational plasma – can generate large magnetic fields much faster than current theorists expected.
“Our theoretical understanding of turbulent dynamo operation has grown steadily for more than half a century,” says Gianluca Gregori, professor of physics in the Department of Physics at Oxford University and experimental director of the project. “Our recent experiments led by TDYNO laser were able to detect for the first time how turbulent dynamo grows in time, allowing us to accurately measure its true growth rate. “
These experiments are part of a joint effort with the TDYNO team to answer key questions discussed in the turbulent dynamo literature, establishing laboratory experiments as part of the study of magnetic turbulent plasmas. The collaboration has built an innovative experimental platform that, together with the power of the OMEGA laser, will allow the team to study the different plasma regimes associated with different astrophysical systems. The experiments are designed using numerical simulations performed by the FLASH code, a publicly available simulation code that can accurately model laser experiments on laboratory plasmas. FLASH is developed by the Flash Center for Computer Science, which recently moved from the University of Chicago to the University of Rochester.
“The ability of high fidelity, predictive modeling with FLASH, and the state-of-the-art diagnostic capabilities of the LLE’s Omega Laser Facility have put our team in a unique position to advance our understanding of cosmic magnetic. fields will become, “says Petros Tzeferacos, associate professor in the Department of Physics and Astronomy at the University of Rochester and senior scientist at the LLE – the project’s simulation lead. Tzeferacos will also serve as director on the Flash Center at Rochester.
“This work paves the way for laboratory investigations of a number of astrophysical processes mediated by magnetic strikes,” says Don Lamb, Robert A. Millikan Distinguished Service Professor of Astronomy and Astronomy at the University Chicago and TDYNO National Principal Investigator Laser User Resource Project (NLUF). “It’s really exciting to see the scientific results that this team’s innovation makes possible.”
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The project was funded by the U.S. Department of Energy, the National Science Foundation, the European Research Council, the Engineering and Physical Sciences Research Council, the DOE National Nuclear Security Administration Laser Consumer Facility, and the DOE Office ASCR Leadership Computing Challenge Science.
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