17:15 〜 19:15
[SIT18-P05] Back-Reaction of Uniform Magnetic Field on Earth’s Core Convection under High Thermal Forcing
キーワード：Magnetoconvection, Supercritical Rayleigh Regimes, Thermal Stable Stratification, Rayleigh-Benard Convection Model
The liquid iron core of the Earth is vigorously convecting due to thermal and chemical buoyancy to generate and sustain geomagnetic fields by dynamo action. Implementing geophysical constraints such as stable stratification and core-mantle boundary (CMB) heterogeneity can substantially modify fluid flow and heat transfer inside the core, resulting in modifying magnetic field morphology. In the present study, a plane layer convection model is used to investigate the evolution of rotating magneto-convection under various levels of buoyancy forcing, from onset to 50 times supercritical, with an axially imposed uniform magnetic field to understand dynamics of convection inside the tangent cylinder. Additionally, a thermally stable stratification is implemented near the top plate to mimic the stable layer near the top of the CMB, as inferred from various geophysical investigations such as seismology, geomagnetism, and mineral physics. Consequently, imposition of stable stratification suppresses the flow to the convectively unstable region at lower buoyancy forcing; however, flow penetrates into the stable layer as thermal forcing is enhanced by 10-50 folds. The uniform magnetic field is incorporated in the axial direction, which poses additional stability to the convective flow at a lower supercritical regime, leading to laminar flow. However, the flow becomes semi-turbulent as thermal forcing is enhanced to higher levels. Furthermore, convective heat transfer in the presence of stable stratification at a high thermal forcing is investigated for penetrative magnetoconvection, and compared with the pure supercritical thermal convection, leading to substantial modification in heat transfer efficiency in the presence of the imposed magnetic field.