Intense bipolar structures from stratified helical dynamos
2014 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 445, no 1, 761-769 p.Article in journal (Refereed) Published
We perform direct numerical simulations of the equations of magnetohydrodynamics with external random forcing and in the presence of gravity. The domain is divided into two parts: a lower layer where the forcing is helical and an upper layer where the helicity of the forcing is zero with a smooth transition in between. At early times, a large-scale helical dynamo develops in the bottom layer. At later times the dynamo saturates, but the vertical magnetic field continues to develop and rises to form dynamic bipolar structures at the top, which later disappear and reappear. Some of the structures look similar to delta spots observed in the Sun. This is the first example of magnetic flux concentrations, owing to strong density stratification, from self-consistent dynamo simulations that generate bipolar, super-equipartition strength, magnetic structures whose energy density can exceeds the turbulent kinetic energy by even a factor of 10.
Place, publisher, year, edition, pages
2014. Vol. 445, no 1, 761-769 p.
dynamo, MHD, sunspots
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-109959DOI: 10.1093/mnras/stu1755ISI: 000343827700056OAI: oai:DiVA.org:su-109959DiVA: diva2:769067