Time-resolved turbulent dynamo in a laser plasma

Archie F.A. Bott, Petros Tzeferacos, Laura Chen, Charlotte A.J. Palmer, Alexandra Rigby, Anthony R. Bell, Robert Bingham, Andrew Birkel, Carlo Graziani, Dustin H. Froula, Joseph Katz, Michel Koenig, Matthew W. Kunz, Chikang Li, Jena Meinecke, Francesco Miniati, Richard Petrasso, Hye Sook Park, Bruce A. Remington, Brian RevilleJ. Steven Ross, Dongsu Ryu, Dmitri Ryutov, Fredrick H. Séguin, Thomas G. White, Alexander A. Schekochihin, Donald Q. Lamb, Gianluca Gregori

Research output: Contribution to journalArticlepeer-review

Abstract

Understanding magnetic-field generation and amplification in turbulent plasma is essential to account for observations of magnetic fields in the universe. A theoretical framework attributing the origin and sustainment of these fields to the so-called fluctuation dynamo was recently validated by experiments on laser facilities in low-magnetic-Prandtl-number plasmas (Pm<1). However, the same framework proposes that the fluctuation dynamo should operate differently when Pm ≳ 1, the regime relevant to many astrophysical environments such as the intracluster medium of galaxy clusters. This paper reports an experiment that creates a laboratory Pm ≳ 1 plasma dynamo. We provide a time-resolved characterization of the plasma's evolution, measuring temperatures, densities, flow velocities, and magnetic fields, which allows us to explore various stages of the fluctuation dynamo's operation on seed magnetic fields generated by the action of the Biermann-battery mechanism during the initial drive-laser target interaction. The magnetic energy in structures with characteristic scales close to the driving scale of the stochastic motions is found to increase by almost three orders of magnitude and saturate dynamically. It is shown that the initial growth of these fields occurs at a much greater rate than the turnover rate of the driving-scale stochastic motions. Our results point to the possibility that plasma turbulence produced by strong shear can generate fields more efficiently at the driving scale than anticipated by idealized magnetohydrodynamics (MHD) simulations of the nonhelical fluctuation dynamo; this finding could help explain the large-scale fields inferred from observations of astrophysical systems.

Original languageEnglish (US)
Article numbere2015729118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number11
DOIs
StatePublished - Mar 16 2021

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Fluctuation dynamo
  • Laboratory astrophysics
  • Magnetic fields

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