Hidden solar magnetic cycle explained with modifications in turbulent induction and pumping  

October 07, 2017

We make use of a solar-like convective dynamo simulation of Käpylä et al. 2016, exhibiting equatorward propagation of the magnetic field, multiple frequencies, and irregular variability, including a missed cycle and complex parity transitions between dipolar and quadrupolar modes, to study the physical causes of such events. We use the test field analysis tool to measure and quantify the effects of turbulence in the generation and evolution of the large-scale magnetic field... 

The Sun, aside from its eleven year sunspot cycle is additionally subject to long term variation in its activity. We make use of a solar-like convective dynamo simulation of Käpylä et al. 2016, exhibiting equatorward propagation of the magnetic field, multiple frequencies, and irregular variability, including a missed cycle and complex parity transitions between dipolar and quadrupolar modes, to study the physical causes of such events. We use the test field analysis tool to measure and quantify the effects of turbulence in the generation and evolution of the large-scale magnetic field. The test-field analysis provides an explanation of the missing surface magnetic cycle in terms of the reduction of part of the alpha effect, the one of the key ingredients for dynamo action. Furthermore, we found an enhancement of downward turbulent pumping during the event to confine some of the magnetic field at the bottom of the convection zone, where local maximum of magnetic energy is observed during the event. At the same time, however, a quenching of the turbulent magnetic diffusivities is observed. For more detailed analysis, we will perform dedicated mean-field modelling with the measured turbulent transport coefficients in the future. more
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