Magnetic Cycles in a Wreath-Building Dynamo Simulation of a Young Solar-type Star

Type Conference Paper
Names Benjamin Brown, M. S. Miesch, M. K. Browning, A. S. Brun, N. J. Nelson, J. Toomre
Proceedings Title Bulletin of the American Astronomical Society
Conference Name American Astronomical Society, AAS Meeting #217, #242.22
Volume 43
Pages 24222
Date January 1, 2011
Library Catalog NASA ADS
Abstract Stars like the Sun build global-scale magnetic fields though dynamo processes in their convection zones. There, global-scale plasma motions couple with rotation and likely drive cycles of magnetic activity, though the exact processes at work in solar and stellar dynamos remain elusive. Observations of younger suns indicate that they rotate quite rapidly, have strong magnetic fields at their surfaces, and show signs of cyclic activity. Here we explore recent 3-D MHD simulations of younger, more rapidly rotating solar-type stars conducted with the anelastic spherical harmonic (ASH) code. These simulations of global-scale convection and dynamo action produce strikingly organized magnetic structures in the bulk of their convection zones. Wreaths of magnetic field fill the convection zone and can undergo regular cycles of polarity reversal. Indeed, we find that cyclic behavior is a common feature throughout the parameter space we have explored. Though these magnetic wreaths can coexist with tachoclines of penetration and shear, they do not rely on that internal boundary layer for their formation or persistence. Tachoclines may play a less critical role in the stellar dynamos of younger Suns than has been supposed in solar dynamo theory.
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