期刊
ASTROPHYSICAL JOURNAL
卷 846, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/aa85a0
关键词
convection; dynamo; magnetohydrodynamics (MHD); methods: numerical; Sun: magnetic fields; sunspots
资金
- National Science Foundation
- Advanced Study Program postdoctoral fellowship at NCAR
- NASA LWSCSW grant [NNX13AJ04A]
- NASA [NNX14AI14G]
- National Science Foundation, on Yellowstone
- NASA [NNX13AJ04A, 473020, 681414, NNX14AI14G] Funding Source: Federal RePORTER
We present a realistic numerical model of sunspot and active region formation based on the emergence of flux bundles generated in a solar convective dynamo. To this end, we use the magnetic and velocity fields in a horizontal layer near the top boundary of the solar convective dynamo simulation to drive realistic radiative-magnetohydrodynamic simulations of the uppermost layers of the convection zone. The main results are as follows. (1) The emerging flux bundles rise with the mean speed of convective upflows and fragment into small-scale magnetic elements that further rise to the photosphere, where bipolar sunspot pairs are formed through the coalescence of the small-scale magnetic elements. (2) Filamentary penumbral structures form when the sunspot is still growing through ongoing flux emergence. In contrast to the classical Evershed effect, the inflow seems to prevail over the outflow in a large part of the penumbra. (3) A well-formed sunspot is a mostly monolithic magnetic structure that is anchored in a persistent deep-seated downdraft lane. The flow field outside the spot shows a giant vortex ring that comprises an inflow below 15Mm depth and an outflow above 15Mm depth. (4) The sunspots successfully reproduce the fundamental properties of the observed solar active regions, including the more coherent leading spots with a stronger field strength, and the correct tilts of bipolar sunspot pairs. These asymmetries can be linked to the intrinsic asymmetries in the magnetic and flow fields adapted from the convective dynamo simulation.
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