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Title: Large-scale magnetic structure formation in three-dimensional magnetohydrodynamic turbulence

Abstract

The inverse cascade of magnetic helicity in three-dimensional magnetohydrodynamic (3D-MHD) turbulence is believed to be one of the processes responsible for large-scale magnetic structure formation in astrophysical systems. In this work, we present an exhaustive set of high-resolution direct numerical simulations of both forced and decaying 3D-MHD turbulence, to understand this structure formation process. It is first shown that an inverse cascade of magnetic helicity in small-scale driven turbulence does not necessarily generate coherent large-scale magnetic structures. The observed large-scale magnetic field, in this case, is severely perturbed by magnetic fluctuations generated by the small-scale forcing. In the decaying case, coherent large-scale structures form similarly to those observed astronomically. Based on the numerical results, the formation of large-scale magnetic structures in some astrophysical systems is suggested to be the consequence of an initial forcing that imparts the necessary turbulent energy into the system, which, after the forcing shuts off, decays to form the large-scale structures. This idea is supported by representative examples, e.g., clusters of galaxies.

Authors:
;  [1]
  1. Max-Planck Institute for Plasmaphysics, Boltzmannstrasse 2, D-85748, Garching bei Muenchen (Germany)
Publication Date:
OSTI Identifier:
22342036
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 778; Journal Issue: 1; 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; ASTROPHYSICS; COMPUTERIZED SIMULATION; DECAY; FLUCTUATIONS; GALAXY CLUSTERS; HELICITY; MAGNETIC FIELDS; MAGNETIC RECONNECTION; MAGNETOHYDRODYNAMICS; RESOLUTION; THREE-DIMENSIONAL CALCULATIONS; TURBULENCE

Citation Formats

Malapaka, Shiva Kumar, and Müller, Wolf-Christian. Large-scale magnetic structure formation in three-dimensional magnetohydrodynamic turbulence. United States: N. p., 2013. Web. doi:10.1088/0004-637X/778/1/21.
Malapaka, Shiva Kumar, & Müller, Wolf-Christian. Large-scale magnetic structure formation in three-dimensional magnetohydrodynamic turbulence. United States. https://doi.org/10.1088/0004-637X/778/1/21
Malapaka, Shiva Kumar, and Müller, Wolf-Christian. 2013. "Large-scale magnetic structure formation in three-dimensional magnetohydrodynamic turbulence". United States. https://doi.org/10.1088/0004-637X/778/1/21.
@article{osti_22342036,
title = {Large-scale magnetic structure formation in three-dimensional magnetohydrodynamic turbulence},
author = {Malapaka, Shiva Kumar and Müller, Wolf-Christian},
abstractNote = {The inverse cascade of magnetic helicity in three-dimensional magnetohydrodynamic (3D-MHD) turbulence is believed to be one of the processes responsible for large-scale magnetic structure formation in astrophysical systems. In this work, we present an exhaustive set of high-resolution direct numerical simulations of both forced and decaying 3D-MHD turbulence, to understand this structure formation process. It is first shown that an inverse cascade of magnetic helicity in small-scale driven turbulence does not necessarily generate coherent large-scale magnetic structures. The observed large-scale magnetic field, in this case, is severely perturbed by magnetic fluctuations generated by the small-scale forcing. In the decaying case, coherent large-scale structures form similarly to those observed astronomically. Based on the numerical results, the formation of large-scale magnetic structures in some astrophysical systems is suggested to be the consequence of an initial forcing that imparts the necessary turbulent energy into the system, which, after the forcing shuts off, decays to form the large-scale structures. This idea is supported by representative examples, e.g., clusters of galaxies.},
doi = {10.1088/0004-637X/778/1/21},
url = {https://www.osti.gov/biblio/22342036}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 778,
place = {United States},
year = {Wed Nov 20 00:00:00 EST 2013},
month = {Wed Nov 20 00:00:00 EST 2013}
}