[P-EM14] Frontiers in solar physics

[PEM14-04] Strong α-quenching in Global Solar Dynamo Simulation

*Ryota Shimada¹, Hideyuki Hotta², Takaaki Yokoyama³ (1.The University of Tokyo, 2.Chiba University, 3.Kyoto University)

Keywords:Magnetohydrodynamics, Solar convection zone, Solar dynamo

Suppression of dynamo effect (α-effect) is investigated using the results of global magnetohydrodynamic (MHD) simulations in the solar convection zone (CZ). The α-effect induces a large-scale magnetic field by helical turbulence. The α-quenching is a candidate saturation mechanism for the solar dynamo, and identifying the details of these mechanisms is one of the key issues in understanding the magnetic field strength produced by the solar dynamo. The α-quenching represents the suppression of the α-effect due to Lorentz force feedback from the magnetic field to the flow field and is considered to be an important mechanism in the determination of the mean field strength produced by the dynamo. There are two major proposed mechanisms: “Normal α-quenching” is based on the feedback from a large-scale magnetic field, while “strong α- quenching” is from a small-scale one. It is not clear which one works in CZ.

We will report the results of the analysis on the α-quenching using the data from global MHD simulations at high magnetic Reynolds, which is almost the same setting as the one by Hotta et al. (2016). We found that the α-effect is suppressed as the large-scale magnetic field increases. The dependences on the large-scale magnetic field of the α-effect and helicities, which contribute to the α-effect are also investigated and reproduce the prediction from the strong α-quenching.

These results suggest that the strong α-quenching works as a dynamo saturation mechanism in the solar CZ at high magnetic Reynolds numbers.