This study shows dependence of the surface diurnal tidal stress on the internal structure of Euro... more This study shows dependence of the surface diurnal tidal stress on the internal structure of Europa. Its purpose is to investigate possibility of cracking of the icy shell. The stress is evaluated under the plausible model of the internal structure constrained by the gravity field data. The possible effective stress at the sub-Jovian point decreases with thickening of the shell,
Physics of the Earth and Planetary Interiors, 1989
The electrical conductivity of sintered polycrystalline olivines (Mg1 - x Fex)2SiO4 (x = 10, 28, ... more The electrical conductivity of sintered polycrystalline olivines (Mg1 - x Fex)2SiO4 (x = 10, 28, 52, 76 and 100%) has been measured at high pressures (2.9-7.0 GPa) and high temperatures (900-1900 K). Measurements at constant temperature and various pressures show that electrical conductivity increases with pressure in the case of high Fe content, whereas it decreases in the case of
Physics of the Earth and Planetary Interiors, 2001
The lateral variations in the thickness of the D″ layer observed by recent global seismology are ... more The lateral variations in the thickness of the D″ layer observed by recent global seismology are suspected to control mantle dynamics. Namiki and Kurita (1999) performed laboratory experiments to explore how undulations of various sizes in the D″ layer affect convection patterns. In addition, we found that the undulation at the lower boundary can induce plumes and that there is
ABSTRACT A numerical simulation of thermal convection induced by internal heating in a three-dime... more ABSTRACT A numerical simulation of thermal convection induced by internal heating in a three-dimensional thin flat box is performed. The upper boundary is held at a constant temperature and the lower boundary is thermally insulated with a uniform internal heating in a fluid layer. We observe hexagonal cells with downwelling at their center in moderate Rayleigh number (RaH
Core formation in terrestrial planets is a complex process, possibly involving several mechanisms... more Core formation in terrestrial planets is a complex process, possibly involving several mechanisms. This paper presents a direct numerical simulation of one of these, the separation of an emulsion of metal in a magma ocean. The model, using a fully Lagrangian approach called the moving particle semi-implicit method, solves the equations of fluid dynamics, including a proper treatment of surface tension. It allows investigation of the balances controlling the distribution of drop size and velocity, in both two- and three-dimensional situations. A scaling analysis where buoyancy is balanced by both surface tension and inertia correctly predicts the average values in these quantities. The full calculation gives an average drop radius of 1.5 cm falling at a velocity of about 30 cm/s. Analysis of the full distribution remains interesting and shows that a significant part of the smallest droplets is entrained upward by the return flow in molten silicate and might be entrained by succeeding thermal convection. In addition, we investigate the conversion of gravitational energy into viscous heating and the thermal equilibration between both phases. We find that viscous heating is essentially produced at the surface of iron drops and that thermal equilibration is dominated by advection. Scaling thermal diffusion to chemical diffusion leads to the estimation that the latter would happen in less than 100 m in the magma ocean.
Recent global seismological observations have revealed lateral variations in the thickness of the... more Recent global seismological observations have revealed lateral variations in the thickness of the D'' layer. We have performed laboratory experiments to explore how undulations of various sizes in the D'' layer affect convection patterns. We find that topography on the lower boundary can induce plumes and that there is a critical height above which topography controls convection patterns. Observed undulations in the D'' layer exceed this critical height, suggesting that they may control mantle convection patterns.
This study shows dependence of the surface diurnal tidal stress on the internal structure of Euro... more This study shows dependence of the surface diurnal tidal stress on the internal structure of Europa. Its purpose is to investigate possibility of cracking of the icy shell. The stress is evaluated under the plausible model of the internal structure constrained by the gravity field data. The possible effective stress at the sub-Jovian point decreases with thickening of the shell,
Physics of the Earth and Planetary Interiors, 1989
The electrical conductivity of sintered polycrystalline olivines (Mg1 - x Fex)2SiO4 (x = 10, 28, ... more The electrical conductivity of sintered polycrystalline olivines (Mg1 - x Fex)2SiO4 (x = 10, 28, 52, 76 and 100%) has been measured at high pressures (2.9-7.0 GPa) and high temperatures (900-1900 K). Measurements at constant temperature and various pressures show that electrical conductivity increases with pressure in the case of high Fe content, whereas it decreases in the case of
Physics of the Earth and Planetary Interiors, 2001
The lateral variations in the thickness of the D″ layer observed by recent global seismology are ... more The lateral variations in the thickness of the D″ layer observed by recent global seismology are suspected to control mantle dynamics. Namiki and Kurita (1999) performed laboratory experiments to explore how undulations of various sizes in the D″ layer affect convection patterns. In addition, we found that the undulation at the lower boundary can induce plumes and that there is
ABSTRACT A numerical simulation of thermal convection induced by internal heating in a three-dime... more ABSTRACT A numerical simulation of thermal convection induced by internal heating in a three-dimensional thin flat box is performed. The upper boundary is held at a constant temperature and the lower boundary is thermally insulated with a uniform internal heating in a fluid layer. We observe hexagonal cells with downwelling at their center in moderate Rayleigh number (RaH
Core formation in terrestrial planets is a complex process, possibly involving several mechanisms... more Core formation in terrestrial planets is a complex process, possibly involving several mechanisms. This paper presents a direct numerical simulation of one of these, the separation of an emulsion of metal in a magma ocean. The model, using a fully Lagrangian approach called the moving particle semi-implicit method, solves the equations of fluid dynamics, including a proper treatment of surface tension. It allows investigation of the balances controlling the distribution of drop size and velocity, in both two- and three-dimensional situations. A scaling analysis where buoyancy is balanced by both surface tension and inertia correctly predicts the average values in these quantities. The full calculation gives an average drop radius of 1.5 cm falling at a velocity of about 30 cm/s. Analysis of the full distribution remains interesting and shows that a significant part of the smallest droplets is entrained upward by the return flow in molten silicate and might be entrained by succeeding thermal convection. In addition, we investigate the conversion of gravitational energy into viscous heating and the thermal equilibration between both phases. We find that viscous heating is essentially produced at the surface of iron drops and that thermal equilibration is dominated by advection. Scaling thermal diffusion to chemical diffusion leads to the estimation that the latter would happen in less than 100 m in the magma ocean.
Recent global seismological observations have revealed lateral variations in the thickness of the... more Recent global seismological observations have revealed lateral variations in the thickness of the D'' layer. We have performed laboratory experiments to explore how undulations of various sizes in the D'' layer affect convection patterns. We find that topography on the lower boundary can induce plumes and that there is a critical height above which topography controls convection patterns. Observed undulations in the D'' layer exceed this critical height, suggesting that they may control mantle convection patterns.
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Papers by Kei Kurita