The role of current helicity in driving solar dynamo

A series of numerical simulations of convective dynamo, with varying grid resolution, with or without explicit magnetic diffusivity and viscosity, are presented and analyzed. It is found that in the simulations, with the increase of Reynolds number, the magnitude of current helicity increases dramatically, whereas the variation of kinetic helicity is very moderate. The competition between the kinetic helicity term and the current helicity term of the alpha coefficient results in an interesting behavior of the large-scale magnetic fields that resembles the ``dynamo-disappear-and-recover" phenomena reported in Hotta et al. 2016 Science paper. Our simulation and analysis suggest that, the role of current helicity first functions to suppress the dynamo, as the convectional $\alpha$-quenching concept states, but then functions to drive the dynamo, instead of quenching it, after a critical Reynolds number is exceeded.