Self-assembly of Shallow Magnetic Spots through Strongly Stratified Turbulence
Abstract
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2013
- DOI:
- 10.1088/2041-8205/776/2/L23
- arXiv:
- arXiv:1306.4915
- Bibcode:
- 2013ApJ...776L..23B
- Keywords:
-
- magnetohydrodynamics: MHD;
- starspots;
- sunspots;
- turbulence;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 6 pages, 5 figures, revised version, ApJL (in press)