Sharp magnetic structures from dynamos with density stratification

Sarah Jabbari; Axel Brandenburg; Nathan Kleeorin; Igor Rogachevskii

doi:10.1093/mnras/stx148

Sharp magnetic structures from dynamos with density stratification

Sarah Jabbari, Axel Brandenburg, Nathan Kleeorin, Igor Rogachevskii

Department of Mechanical Engineering

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

Recent direct numerical simulations (DNS) of large-scale turbulent dynamos in strongly stratified layers have resulted in surprisingly sharp bipolar structures at the surface. Here, we present new DNS of helically and non-helically forced turbulence with and without rotation and compare with corresponding mean-field simulations (MFS) to show that these structures are a generic outcome of a broader class of dynamos in density-stratified layers. The MFS agree qualitatively with the DNS, but the period of oscillations tends to be longer in the DNS. In both DNS and MFS, the sharp structures are produced by converging flows at the surface and might be driven in non-linear stage of evolution by the Lorentz force associated with the large-scale dynamo-driven magnetic field if the dynamo number is at least 2.5 times supercritical.

Original language	English
Pages (from-to)	2753-2765
Number of pages	13
Journal	Monthly Notices of the Royal Astronomical Society
Volume	467
Issue number	3
DOIs	https://doi.org/10.1093/mnras/stx148
State	Published - 1 Jun 2017

Keywords

Dynamo
Sunspots
Turbulence

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1093/mnras/stx148

Cite this

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title = "Sharp magnetic structures from dynamos with density stratification",

abstract = "Recent direct numerical simulations (DNS) of large-scale turbulent dynamos in strongly stratified layers have resulted in surprisingly sharp bipolar structures at the surface. Here, we present new DNS of helically and non-helically forced turbulence with and without rotation and compare with corresponding mean-field simulations (MFS) to show that these structures are a generic outcome of a broader class of dynamos in density-stratified layers. The MFS agree qualitatively with the DNS, but the period of oscillations tends to be longer in the DNS. In both DNS and MFS, the sharp structures are produced by converging flows at the surface and might be driven in non-linear stage of evolution by the Lorentz force associated with the large-scale dynamo-driven magnetic field if the dynamo number is at least 2.5 times supercritical.",

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AU - Jabbari, Sarah

AU - Brandenburg, Axel

AU - Kleeorin, Nathan

AU - Rogachevskii, Igor

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AB - Recent direct numerical simulations (DNS) of large-scale turbulent dynamos in strongly stratified layers have resulted in surprisingly sharp bipolar structures at the surface. Here, we present new DNS of helically and non-helically forced turbulence with and without rotation and compare with corresponding mean-field simulations (MFS) to show that these structures are a generic outcome of a broader class of dynamos in density-stratified layers. The MFS agree qualitatively with the DNS, but the period of oscillations tends to be longer in the DNS. In both DNS and MFS, the sharp structures are produced by converging flows at the surface and might be driven in non-linear stage of evolution by the Lorentz force associated with the large-scale dynamo-driven magnetic field if the dynamo number is at least 2.5 times supercritical.

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Sharp magnetic structures from dynamos with density stratification

Abstract

Keywords

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