3D MHD Simulation of Non-convective Spruit's Dynamo - Application to Polar Field Amplification in the Sun -

Masada Youhei, ymasada@harbor.kobe-u.ac.jp, Department of Computational Science, Kobe University, Japan

Abstract
Spruit (2002) proposed a new dynamo model , called "Spruit's Dynamo", which can operate in convectively stable region inside stars. Though there exists numerical works which studied non-linear developments of the Spruit's dynamo, we have still no consensus on its non-linear properties. We present, in this talk, results of our 3D MHD simulation on this non-convective Spruit's dynamo. As the numerical setting, we adopt a differentially rotating cylinder which models a local portion around the rotation axis of the stellar interior. It is found from our numerical models that the Spruit's dynamo does work in the differentially rotating system regardless of whether the net non-zero magnetic flux is imposed initially on the system or not. In addition, we find that the field reversal takes place at the non-linear saturated stage for the model with a larger viscosity than the critical value. We finally discuss the application of the Spruit' dynamo to the polar field amplification of the Sun and the young G-type stars.