Spontaneous magnetization of collisionless plasma

Muni Zhou, Vladimir Zhdankin, Matthew W. Kunz, Nuno F. Loureiro, Dmitri A. Uzdensky

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


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.

Original languageEnglish (US)
Article numbere2119831119
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number19
StatePublished - May 10 2022

All Science Journal Classification (ASJC) codes

  • General


  • Weibel instability
  • dynamo
  • magnetogenesis
  • seed magnetic fields
  • shear flow


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