Magnetogenesis in a Collisionless Plasma: From Weibel Instability to Turbulent Dynamo
Name
24ja025_full.pdf
Size
13.41 MB
Format
Adobe PDF
Checksum (MD5)
0055a15a5e35a0069e8071f63c9f962b
Author(s)
Zhou, Muni
Zhdankin, Vladimir
Kunz, Matthew W.
Loureiro, Nuno F.
Uzdensky, Dmitri A.
Date Issued
June 2024
Journal
Astrophysical Journal
Publisher
AAS and IOP
Abstract
We report on a first-principles numerical and theoretical study of plasma dynamo in a fully kinetic framework. By applying an external mechanical force to an initially unmagnetized plasma, we develop a self-consistent treatment of the generation of "seed" magnetic fields, the formation of turbulence, and the inductive amplification of fields by the fluctuation dynamo. Driven large-scale motions in an unmagnetized, weakly collisional plasma are subject to strong phase mixing, which leads to the development of thermal pressure anisotropy. This anisotropy triggers the Weibel instability, which produces filamentary "seed" magnetic fields on plasma-kinetic scales. The plasma is thereby magnetized, enabling efficient stretching and folding of the fields by the plasma motions and the development of Larmor-scale kinetic instabilities such as the firehose and mirror. The scattering of particles off the associated microscale magnetic fluctuations provides an effective viscosity, regulating the field morphology and turbulence. During this process, the seed field is further amplified by the fluctuation dynamo until energy equipartition with the turbulent flow is reached. By demonstrating that equipartition magnetic fields can be generated from an initially unmagnetized plasma through large-scale turbulent flows, this work has important implications for the origin and amplification of magnetic fields in the intracluster and intergalactic mediums.
Description
Submitted for publication in Astrophysical Journal
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.3847/1538-4357/ad0b0f
