Non-kinematic flux-transport dynamos with variable meridional flow

A single counter clockwise flow cell is the assumption underlying most flux-transport dynamo models to date. On the other hand, global 3D simulations of the solar convection zone by Miesch et al. indicate that the meridional flow is strongly variable and shows at a given time a multi-cellular flow structure, with only the long term average reflecting a more regular flow field. We investigate the influence of such a highly time variable meridional flow on a flux-transport dynamo model. In our model the differential rotation and meridional flow are driven self-consistently through a parameterization of the Reynolds-stress (A-effect) and also macroscopic Lorentz-force feedback is considered. We achieve the time variable flow by adding random fluctuations with a given correlation time and length scale to both components of the turbulent angular momentum flux. We find that a significant amount of random fluctuations can be tolerated before the dynamo loses its coherence, provided that the correlation time scale of the random component is significantly shorter than the cycle length. Stronger constraints on the amplitude of random fluctuations come from helioseismic constraints on the variability of differential rotation.