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Author Beaudoin, Patrice ♦ Simard, Corinne ♦ Cossette, Jean-François ♦ Charbonneau, Paul
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ CONVECTION ♦ DETECTION ♦ ELECTROMOTIVE FORCE ♦ HYPOTHESIS ♦ INTERACTIONS ♦ MAGNETIC FIELDS ♦ MAGNETOHYDRODYNAMICS ♦ MEAN-FIELD THEORY ♦ PERIODICITY ♦ PHOTOSPHERE ♦ ROTATION ♦ SIMULATION ♦ SOLAR ACTIVITY ♦ SPACE ♦ SUN
Abstract The 11 year solar activity cycle is the most prominent periodic manifestation of the magnetohydrodynamical (MHD) large-scale dynamo operating in the solar interior, yet longer and shorter (quasi-) periodicities are also present. The so-called “quasi-biennial” signal appearing in many proxies of solar activity has been gaining increasing attention since its detection in p -mode frequency shifts, which suggests a subphotospheric origin. A number of candidate mechanisms have been proposed, including beating between co-existing global dynamo modes, dual dynamos operating in spatially separated regions of the solar interior, and Rossby waves driving short-period oscillations in the large-scale solar magnetic field produced by the 11 year activity cycle. In this article, we analyze a global MHD simulation of solar convection producing regular large-scale magnetic cycles, and detect and characterize shorter periodicities developing therein. By constructing kinematic mean-field α {sup 2}Ω dynamo models incorporating the turbulent electromotive force (emf) extracted from that same simulation, we find that dual-dynamo behavior materializes in fairly wide regions of the model’s parameters space. This suggests that the origin of the similar behavior detected in the MHD simulation lies with the joint complexity of the turbulent emf and differential rotation profile, rather that with dynamical interactions such as those mediated by Rossby waves. Analysis of the simulation also reveals that the dual dynamo operating therein leaves a double-period signature in the temperature field, consistent with a dual-period helioseismic signature. Order-of-magnitude estimates for the magnitude of the expected frequency shifts are commensurate with helioseismic measurements. Taken together, our results support the hypothesis that the solar quasi-biennial oscillations are associated with a secondary dynamo process operating in the outer reaches of the solar convection zone.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-08-01
Publisher Place United States
Journal Astrophysical Journal
Volume Number 826
Issue Number 2


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