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Self-assembly of shallow magnetic spots through strongly stratified turbulence
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.ORCID iD: 0000-0002-7304-021X
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
2013 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 776, no 2, L23- p.Article in journal (Refereed) Published
Abstract [en]

Recent studies have demonstrated that in fully developed turbulence, the effective magnetic pressure of a large-scale field (non-turbulent plus turbulent contributions) can become negative. In the presence of strongly stratified turbulence, this was shown to lead to a large-scale instability that produces spontaneous magnetic flux concentrations. Furthermore, using a horizontal magnetic field, elongated flux concentrations with a strength of a few percent of the equipartition value were found. Here we show that a uniform vertical magnetic field leads to circular magnetic spots of equipartition field strengths. This could represent a minimalistic model of sunspot formation and highlights the importance of two critical ingredients: turbulence and strong stratification. Radiation, ionization, and supergranulation may be important for realistic simulations, but are not critical at the level of a minimalistic model of magnetic spot formation.

Place, publisher, year, edition, pages
2013. Vol. 776, no 2, L23- p.
Keyword [en]
magnetohydrodynamics (MHD), starspots, sunspots, turbulence
National Category
Other Physics Topics
URN: urn:nbn:se:kth:diva-133523DOI: 10.1088/2041-8205/776/2/L23ISI: 000325490200006ScopusID: 2-s2.0-84885358490OAI: diva2:662402
EU, European Research Council, 227952Swedish Research Council, 621-2011-5076 2012-5797

QC 20131107

Available from: 2013-11-07 Created: 2013-11-06 Last updated: 2013-11-07Bibliographically approved

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Brandenburg, AxelKleeorin, NathanRogachevskii, Igor
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