Dynamo Action and Meridional Circulation Dynamics in Eulag-MHD Global 3D MHD Simulations of Solar Convection

Abstract:

The steady advance in computer power has finally enabled us to explore the solar dynamo problem by means of 3D global magnetohydrodynamical (MHD) simulations of the convection zone.
Using the EULAG-MHD code, we have succeeded in producing simulations of the Sun's magnetic activity cycles that resemble the observed evolutionary patterns of the large-scale solar magnetic field. In these simulations the anelastic ideal MHD equations are solved in a thick, rotating shell of electrically conducting fluid, under solar-like stratification and thermal forcing. Since these simulations are fully dynamical in all time and spatial resolved scales, they achieve highly turbulent regimes and naturally produce variable amplitude solutions.
We have recently been able to produce a simulation that spans for 1650 years and that produced 40 complete sunspot like cycles, the longest of its kind so far.
This allows to perform statistical studies and establish direct comparisons with the observed solar cycle. Some of the main similarities and differences between the statistical properties of simulated and observed cycles are presented here (e.g. evidence for Gnevyshev-Ohl patterns, Gleissberg modulation or hemispheric coupling). Additionally, by studying the behaviour of the large scale flows in the simulation (differential rotation and meridional circulation) we also find evidence for solar cycle modulation of the deep equatorward flow in the meridional circulation. This result is briefly discussed as well as its implications for current helioseismic measurement methodologies and for classical kinematic mean-field flux transport dynamo simulations.