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research article

Small-scale dynamo with finite correlation times

Carteret, Yann
•
Schleicher, Dominik
•
Schober, Jennifer  
June 27, 2023
Physical Review E

Fluctuation dynamos occur in most turbulent plasmas in astrophysics and are the prime candidates for amplifying and maintaining cosmic magnetic fields. A few analytical models exist to describe their behavior, but they are based on simplifying assumptions. For instance, the well-known Kazantsev model assumes an incompressible flow that is 8-correlated in time. However, these assumptions can break down in the interstellar medium as it is highly compressible and the velocity field has a finite correlation time. Using the renewing flow method developed by Bhat and Subramanian (2014), we aim to extend Kazantsev's results to a more general class of turbulent flows. The cumulative effect of both compressibility and finite correlation time over the Kazantsev spectrum is studied analytically. We derive an equation for the longitudinal two-point magnetic correlation function in real space to first order in the correlation time ⠃ and for an arbitrary degree of compressibility (DOC). This generalized Kazantsev equation encapsulates the original Kazantsev equation. In the limit of small Strouhal numbers St & PROP; ⠃ we use the Wentzel-Kramers-Brillouin approximation to derive the growth rate and scaling of the magnetic power spectrum. We find the result that the Kazantsev spectrum is preserved, i.e., Mk(k) & SIM; k3/2. The growth rate is also negligibly affected by the finite correlation time; however, it is reduced by the finite magnetic diffusivity and the DOC together.

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Type
research article
DOI
10.1103/PhysRevE.107.065210
Web of Science ID

WOS:001035328300008

Author(s)
Carteret, Yann
Schleicher, Dominik
Schober, Jennifer  
Date Issued

2023-06-27

Publisher

AMER PHYSICAL SOC

Published in
Physical Review E
Volume

107

Issue

6

Article Number

065210

Subjects

Physics, Fluids & Plasmas

•

Physics, Mathematical

•

Physics

•

magnetic-fields

•

turbulent dynamo

•

interstellar

•

galaxies

•

intermittency

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LASTRO  
Available on Infoscience
August 14, 2023
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/199758
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