World’s largest turbulent simulation reveals energy flow in astrophysical plasmas — ScienceDaily

Researchers have discovered a previously hidden heating mechanism that helps explain how the atmosphere around the Sun, called the solar corona, can be much hotter than the surface of the Sun that emits it.

Discoveries at the United States Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) could improve the handling of many astronomical puzzles, such as the formation of stars, the origin of supergravity in the universe, and the ability of to predict the area that may explode. weather events that can disrupt cell phone service and shut down the Earth’s power grid. Understanding the heating process also has implications for fusion research.


“Our direct numerical simulation is the first to provide a detailed description of this heating mechanism in 3D space,” said Chuanfei Dong, a physicist at PPPL and Princeton University who revealed the process by channel 200 million hours of computer time for the world’s largest simulation. its kind. “Current telescope and spacecraft instruments may not have high enough resolution to detect processes occurring at small scales,” said Dong, who details the breakthrough in the paper. Advances in Science.

The hidden ingredient is a process called “magnetic reconnection” that separates and strongly rejoins the magnetic fields of plasma, the soup of electrons and atomic nuclei that make up the solar atmosphere. Dong’s simulation revealed how the rapid entanglement of the magnetic field transforms a large perturbation force into a small internal force. As a result the turbulent energy is effectively converted to thermal energy on a small scale, thus heating up the corona.

“Think of putting cream in coffee,” Dong said. “Drops of cream soon turn into whorls and thin curls. Similarly, gravity creates thin sheets of electric current that break due to recombination. This process is facilitate the flow of energy from the large to the small, making the process more efficient. in the chaos of the sun than previously thought.”

While the recombination process is slower when the turbulence rate is faster, recombination will not affect the transfer of energy across the scale, he said. But when the rate of convergence is sufficiently faster than the normal rate of attrition, the convergence can move the rate to smaller scales more efficiently.

It does this by breaking and recombining magnetic field lines to produce chains of tiny twisted lines called plasmoids. The paper says that this changes the understanding of energy flow that has been widely accepted for more than half a century. The new finding links the rate of energy transfer to how fast the plasmoids grow, enhancing energy transfer from large to small and strongly heating the corona at these scales.

The new discovery shows the regime with the largest magnetic Reynolds number as in the solar corona. The large number marks a new high-energy transmission rate of turbulence. “The higher the magnetic Reynolds number, the more efficient the recirculating energy transfer is,” said Dong, who is moving to Boston University to take up an academic position.

200 million hours

“Chuanfei has created the world’s largest scrambler of its kind that has taken over 200 million computer CPUs. [central processing units] at the NASA Advanced Supercomputing (NAS) facility,” said PPPL physicist Amitava Bhattacharjee, a Princeton professor of astrophysics who supervised the research. of the turbulent energy flow controlled by the growth of plasmoids.

“His paper in a high-impact journal Advances in Science completes the computer program he started with his earlier 2D results published in Physical Examination Letters. These papers form a coda to the remarkable work that Chuanfei has done as a member of the Princeton Center for Heliophysics,” a joint institute of Princeton and PPPL. “Thanks to PPPL LDRD. [Laboratory Directed Research & Development] helped this work, and the NASA High-End Computing (HEC) program for its generous allocation of computing time.”

The impact of this discovery on star systems across different scales can be explored with future spacecraft and telescopes. Unraveling the energy transfer process at scale will be key to solving important mysteries of the universe, the paper said.

Funding for this paper came from the DOE Office of Science (FES) and NASA, with computing resources provided by NASA HEC as well as the National Computer Science Research Center, DOE Office of Science User Center , and Computational Center and supported by NSF. Information Management Laboratory. Co-authors of the paper were researchers at PPPL, Princeton and Columbia Universities, and NASA Ames Research Center.

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Resources provided by DOE/Princeton Plasma Physics Laboratory. The first was written by John Greenwald. Note: Content may be edited for style and length.

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