Sharp magnetic structures from dynamos with density stratification

Jabbari, SarahStockholms universitet,KTH,Nordic Institute for Theoretical Physics NORDITA,Monash Univ, Australia; Stockholm Univ, Sweden,Nordiska institutet för teoretisk fysik (Nordita),Institutionen för astronomi,Monash University, Australia (author)

QC 20170517
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.

Brandenburg, AxelStockholms universitet,KTH,Nordic Institute for Theoretical Physics NORDITA,Stockholm Univ, Sweden; Univ Colorado, USA; Lab Atmospher & Space Phys, USA,Nordiska institutet för teoretisk fysik (Nordita),Institutionen för astronomi,University of Colorado, USA; Laboratory for Atmospheric and Space Physics, USA(Swepub:su)brandenb (author)
Kleeorin, NathanStockholms universitet,KTH,Nordic Institute for Theoretical Physics NORDITA,Stockholm Univ, Sweden; Ben Gurion Univ Negev, Israel,Nordiska institutet för teoretisk fysik (Nordita),Ben-Gurion University of the Negev, Israel(Swepub:kth)u10pszpw (author)
Rogachevskii, IgorStockholms universitet,KTH,Nordic Institute for Theoretical Physics NORDITA,Stockholm Univ, Sweden; Ben Gurion Univ Negev, Israel,Nordiska institutet för teoretisk fysik (Nordita),Ben-Gurion University of the Negev, Israel(Swepub:su)iroga (author)
KTHNordic Institute for Theoretical Physics NORDITA (creator_code:org_t)

In:Monthly notices of the Royal Astronomical Society: OXFORD UNIV PRESS467:3, s. 2753-27650035-87111365-2966

By the author/editor: Jabbari, Sarah; Brandenburg, Axe ...; Kleeorin, Nathan; Rogachevskii, Ig ...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Astronomy Astrop ...

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