Simulation Study of Energy Conversion Process in Magnetohydrodynamic Turbulence Due to Magnetorotational Instability(Gases, Plasmas and Electric Discharges)

概要

論文の詳細を見る
Three dimensional local simulation was performed to investigate the energy conversion and the dynamo action in the magnetohydrodynamic (MHD) turbulence due to the magnetorotational instability (MRI) in a differentially rotating disk, using Arbitrary Lagrangian Eulerian method. As a result, it was found that the turbulence plays a role to convert the magnetic energy to the kinetic energy, if the shear parameter q defined by -din Ω/dln R is less than 2.3, where Ω and R are the angular velocity and the disk radius, respectively. It means that amplification of the magnetic energy in the MRI is mainly due to the twisting effect of differential rotation rather than a result of the turbulent dynamo action. When q ≥ 2.5, the energy conversion rate from the kinetic energy to the magnetic energy is switched to positive, because low modes, which are destabilized by the Rayleigh instability, can work for the turbulent dynamo. On the other hand, it is also revealed that, the a-dynamo effect exists at least for q ≥ 0.75, although the contribution to the amplification of the magnetic energy is very small. From these results, it can be concluded that, even though the MRI is able to amplify the magnetic energy, the turbulence due to the MRI is less effective as a driver of the conventional dynamo process, unless the Rayleigh instability arises.
社団法人日本物理学会の論文
2004-01-15