Mean-field Modeling of Global Solar Dynamo based on Cartesian DNSs of Convective Dynamo

by Youhei Masada (Aichi University of Education, Kariy, Japan)

Tuesday 13 Sept 2022, 10:00 → 11:00 Europe/Stockholm

https://stockholmuniversity.zoom.us/j/940229961

In a rigidly-rotating MHD system with convective turbulence, a large-scale dynamo, categorized as the α2-type, can be excited when the spin rate is large enough. In the first part of my talk, the rotational dependence of the α2-type dynamo and the cause of it are explored by mean-field (MF) dynamo models coupled with direct numerical simulations (DNSs) of MHD convections. Our DNS models show that the α2-type dynamo is excited when Ro is smaller than about 0.1 where Ro is the Rossby number defined with the volume-averaged mean convective velocity. From the corresponding MF models, we demonstrate that the rotational dependence of the α2-type dynamo is mainly due to the change in the magnitude of the turbulent magnetic diffusion. With increasing the spin rate, the turbulent magnetic diffusion weakens while the α-effect remains essentially unchanged over the convection zone, providing the critical point for the excitation of the large-scale dynamo. With these characteristics of the turbulent EMF in mind and taking account of the solar rotation profile deduced from the helioseismic diagnostics, we also develop a global solar MF dynamo model. In the later part of my talk, the modeling procedure and the spatio-temporal properties of the magnetic field obtained in our model are discussed in detail.
 

Masada_2022-Sep-13.mp4