Journal
ASTROPHYSICAL JOURNAL
Volume 785, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/785/2/90
Keywords
convection; magnetohydrodynamics (MHD); radiative transfer; sunspots
Categories
Funding
- National Science Foundation [OCI-1053575]
- National Institute for Computational Sciences (NICS) [TG-AST100005]
- NASA [NNM07AA01C]
- Lockheed Martin SDO/HMI from Stanford University through Stanford University [25284100-26967, NAS5-02139]
- UK Space Agency [ST/J001732/1] Funding Source: researchfish
- Directorate For Geosciences
- Div Atmospheric & Geospace Sciences [0929367] Funding Source: National Science Foundation
Ask authors/readers for more resources
We present numerical simulations of active region scale flux emergence covering a time span of up to 6 days. Flux emergence is driven by a bottom boundary condition that advects a semi-torus of magnetic field with 1.7x10(22) Mx flux into the computational domain. The simulations show that, even in the absence of twist, the magnetic flux is able the rise through the upper 15.5 Mm of the convection zone and emerge into the photosphere to form spots. We find that spot formation is sensitive to the persistence of upflows at the bottom boundary footpoints, i.e., a continuing upflow would prevent spot formation. In addition, the presence of a torus-aligned flow (such flow into the retrograde direction is expected from angular momentum conservation during the rise of flux ropes through the convection zone) leads to a significant asymmetry between the pair of spots, with the spot corresponding to the leading spot on the Sun being more axisymmetric and coherent, but also forming with a delay relative to the following spot. The spot formation phase transitions directly into a decay phase. Subsurface flows fragment the magnetic field and lead to intrusions of almost field free plasma underneath the photosphere. When such intrusions reach photospheric layers, the spot fragments. The timescale for spot decay is comparable to the longest convective timescales present in the simulation domain. We find that the dispersal of flux from a simulated spot in the first two days of the decay phase is consistent with self-similar decay by turbulent diffusion.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available