@article{9d5f84dc3231487f9b630224d0b8c6e2,
title = "Spontaneous magnetization of collisionless plasma",
abstract = "We study within a fully kinetic framework the generation of “seed” magnetic fields through the Weibel instability, driven in an initially unmagnetized plasma by a large-scale shear force. We develop an analytical model that describes the development of thermal pressure anisotropy via phase mixing, the ensuing exponential growth of magnetic fields in the linear Weibel stage, and the saturation of the Weibel instability when the seed magnetic fields become strong enough to instigate gyromotion of particles and thereby inhibit their free-streaming. The predicted scaling dependencies of the saturated fields on key parameters (e.g., ratio of system scale to electron skin depth and forcing amplitude) are confirmed by two-dimensional and three-dimensional particle-in-cell simulations of an electron-positron plasma. This work demonstrates the spontaneous magnetization of a collisionless plasma through large-scale motions as simple as a shear flow and therefore has important implications for magnetogenesis in dilute astrophysical systems.",
keywords = "Weibel instability, dynamo, magnetogenesis, seed magnetic fields, shear flow",
author = "Muni Zhou and Vladimir Zhdankin and Kunz, {Matthew W.} and Loureiro, {Nuno F.} and Uzdensky, {Dmitri A.}",
note = "Funding Information: ACKNOWLEDGMENTS. We thank J. Juno, F. Rincon, A. A. Schekochihin, and D. A. St-Onge for insightful discussions and the editor and two anonymous referees for comments that improved the manuscript. Support for N.F.L. and M.Z. was provided by NSF CAREER Award 1654168 and by NASA Award NNH19ZA001N-FINESST. Support for V.Z. was provided by NASA Hubble Fellowship Grant HST-HF2-51426.001-A, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under Contract NAS5-26555. Support for M.W.K. was provided by NSF CAREER Award 1944972. Support for D.A.U. was provided by NASA Grants NNX17AK57G and 80NSSC20K0545 and NSF Grant AST-1806084. The completion of this work was aided by the generous hospitality of the Kavli Institute for Theoretical Physics in Santa Barbara, supported in part by NSF Grant PHY-1748958. The work used the Extreme Science and Engineering Discovery Environment, which is supported by NSF GrantACI-1548562. The simulations presented in this work were performed on the supercomputer Stampede2 at the Texas Advanced Computer Center through Allocation TG-PHY140041. Publisher Copyright: Copyright {\textcopyright} 2022 the Author(s).",
year = "2022",
month = may,
day = "10",
doi = "10.1073/pnas.2119831119",
language = "English (US)",
volume = "119",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
issn = "0027-8424",
publisher = "National Academy of Sciences",
number = "19",
}