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Title: GROWTH OF A LOCALIZED SEED MAGNETIC FIELD IN A TURBULENT MEDIUM

Abstract

Turbulence dynamo deals with the amplification of a seed magnetic field in a turbulent medium and has been studied mostly for uniform or spatially homogeneous seed magnetic fields. However, some astrophysical processes (e.g., jets from active galaxies, galactic winds, or ram-pressure stripping in galaxy clusters) can provide localized seed magnetic fields. In this paper, we numerically study amplification of localized seed magnetic fields in a turbulent medium. Throughout the paper, we assume that the driving scale of turbulence is comparable to the size of the system. Our findings are as follows. First, turbulence can amplify a localized seed magnetic field very efficiently. The growth rate of magnetic energy density is as high as that for a uniform seed magnetic field. This result implies that magnetic field ejected from an astrophysical object can be a viable source of a magnetic field in a cluster. Second, the localized seed magnetic field disperses and fills the whole system very fast. If turbulence in a system (e.g., a galaxy cluster or a filament) is driven at large scales, we expect that it takes a few large-eddy turnover times for the magnetic field to fill the whole system. Third, growth and turbulence diffusion of amore » localized seed magnetic field are also fast in high magnetic Prandtl number turbulence. Fourth, even in decaying turbulence, a localized seed magnetic field can ultimately fill the whole system. Although the dispersal rate of the magnetic field is not fast in purely decaying turbulence, it can be enhanced by an additional forcing.« less

Authors:
;  [1]
  1. Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of)
Publication Date:
OSTI Identifier:
22086423
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLIFICATION; ASTRONOMY; ASTROPHYSICS; DIFFUSION; ENERGY DENSITY; FILAMENTS; GALAXIES; GALAXY CLUSTERS; INTERSTELLAR MAGNETIC FIELDS; JETS; MAGNETOHYDRODYNAMICS; PRANDTL NUMBER; STELLAR WINDS; TURBULENCE

Citation Formats

Cho, Jungyeon, and Yoo, Hyunju, E-mail: jcho@cnu.ac.kr. GROWTH OF A LOCALIZED SEED MAGNETIC FIELD IN A TURBULENT MEDIUM. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/2/91.
Cho, Jungyeon, & Yoo, Hyunju, E-mail: jcho@cnu.ac.kr. GROWTH OF A LOCALIZED SEED MAGNETIC FIELD IN A TURBULENT MEDIUM. United States. doi:10.1088/0004-637X/759/2/91.
Cho, Jungyeon, and Yoo, Hyunju, E-mail: jcho@cnu.ac.kr. Sat . "GROWTH OF A LOCALIZED SEED MAGNETIC FIELD IN A TURBULENT MEDIUM". United States. doi:10.1088/0004-637X/759/2/91.
@article{osti_22086423,
title = {GROWTH OF A LOCALIZED SEED MAGNETIC FIELD IN A TURBULENT MEDIUM},
author = {Cho, Jungyeon and Yoo, Hyunju, E-mail: jcho@cnu.ac.kr},
abstractNote = {Turbulence dynamo deals with the amplification of a seed magnetic field in a turbulent medium and has been studied mostly for uniform or spatially homogeneous seed magnetic fields. However, some astrophysical processes (e.g., jets from active galaxies, galactic winds, or ram-pressure stripping in galaxy clusters) can provide localized seed magnetic fields. In this paper, we numerically study amplification of localized seed magnetic fields in a turbulent medium. Throughout the paper, we assume that the driving scale of turbulence is comparable to the size of the system. Our findings are as follows. First, turbulence can amplify a localized seed magnetic field very efficiently. The growth rate of magnetic energy density is as high as that for a uniform seed magnetic field. This result implies that magnetic field ejected from an astrophysical object can be a viable source of a magnetic field in a cluster. Second, the localized seed magnetic field disperses and fills the whole system very fast. If turbulence in a system (e.g., a galaxy cluster or a filament) is driven at large scales, we expect that it takes a few large-eddy turnover times for the magnetic field to fill the whole system. Third, growth and turbulence diffusion of a localized seed magnetic field are also fast in high magnetic Prandtl number turbulence. Fourth, even in decaying turbulence, a localized seed magnetic field can ultimately fill the whole system. Although the dispersal rate of the magnetic field is not fast in purely decaying turbulence, it can be enhanced by an additional forcing.},
doi = {10.1088/0004-637X/759/2/91},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}