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Cycles and cycle modulations

Published online by Cambridge University Press:  05 July 2012

Axel Brandenburg  and
Gustavo Guerrero
Axel Brandenburg
Affiliation:
Nordita, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden email: brandenb@nordita.org Department of Astronomy, Stockholm University, SE-10691 Stockholm, Sweden
Gustavo Guerrero
Affiliation:
Nordita, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden email: brandenb@nordita.org Solar Physics, HEPL, Stanford University, Stanford, CA 94305-4085, USA
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Abstract

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Some selected concepts of the solar activity cycle are reviewed. Cycle modulations through a stochastic α effect are being identified with limited scale separation ratios. Three-dimensional turbulence simulations with helicity and shear are compared at two different scale separation ratios. In both cases the level of fluctuations shows relatively little variation with the dynamo cycle. Prospects for a shallow origin of sunspots are discussed in terms of the negative effective magnetic pressure instability. Tilt angles of bipolar active regions are discussed as a consequence of shear rather than the Coriolis force.

Keywords

MHDturbulenceSun: activitySun: magnetic fieldssunspots

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