Ulrich Hansen

Imperial College London

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Temporal variations in the convective style of planetary mantles

Earth and Planetary Science Letters (2006)

Alexander Loddoch Claudia Stein Ulrich Hansen

10.1016/j.epsl.2006.08.026

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Citations (30)

A finite-volume solution method for thermal convection and dynamo problems in spherical shells

Geophysical Journal International (2005)

Helmut Harder Ulrich Hansen

We present a novel application of a finite-volume technique to the numerical simulation of thermal convection within a rapidly rotating spherical shell. The performance of the method is extensively tested against a known standard solution at moderate Ekman number. Models at lower Ekman number demonstrate the potential of the method in a parameter range more appropriate to the flow in the molten metallic core of planetary interiors. In addition we present results for the magnetohydrodynamic dynamo problem. In order to avoid the need to solve for the magnetic field in the exterior, we use an approximate magnetic boundary condition. Compared with the geophysically relevant case of insulating boundaries, it is shown that the qualitative structures of the flow and the magnetic field are similar. However, a more quantitative comparison indicates that mean flow velocity and mean magnetic field strength are affected by the boundary conditions by about 20 per cent.

Ekman number

Spherical shell

10.1111/j.1365-246x.2005.02560.x

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Citations (72)

A benchmark comparison for mantle convection codes

Geophysical Journal International (1989)

B. Blankenbach F. H. Busse Ulrich R. Christensen L. Cserepes D. Gunkel

We have carried out a comparison study for a set of benchmark problems which are relevant for convection in the Earth's mantle. The cases comprise steady isoviscous convection, variable viscosity convection and time-dependent convection with internal heating. We compare Nusselt numbers, velocity, temperature, heat-flow, topography and geoid data. Among the applied codes are finite-difference, finite-element and spectral methods. In a synthesis we give best estimates of the 'true' solutions and ranges of uncertainty. We recommend these data for the validation of convection codes in the future.

Internal heating

Benchmark (surveying)

10.1111/j.1365-246x.1989.tb05511.x

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Citations (296)

Numerical Parameter Study of the Rotational Influence on the 'Metal Rain Scenario'

AGUFM (2012)

A. Möller Ulrich Hansen

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Numerical investigation of a layered temperature-dependent viscosity convection in comparison to convection with a full temperature dependence

Physics of The Earth and Planetary Interiors (2013)

Claudia Stein Ulrich Hansen

Convection cell

Rayleigh–Bénard convection

10.1016/j.pepi.2013.11.004

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Citations (6)

Different Tectonic Styles in a Self-Consistent Mantle Convection Model

AGUFM (2002)

Claudia Stein Ulrich Hansen

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Effects of Earth's rotation on the early differentiation of a terrestrial magma ocean

Journal of Geophysical Research Solid Earth (2015)

Christian Maas Ulrich Hansen

Abstract Similar to other terrestrial planets like Moon and Mars, Earth experienced a magma ocean period about 4.5 billion years ago. On Earth differentiation processes in the magma ocean set the initial conditions for core formation and mantle evolution. During the magma ocean period Earth was rotating significantly faster than today. Further, the viscosity of the magma was low, thus that planetary rotation potentially played an important role for differentiation. However, nearly all previous studies neglect rotational effects. All in all, our results suggest that planetary rotation plays an important role for magma ocean crystallization. We employ a 3‐D numerical model to study crystal settling in a rotating and vigorously convecting early magma ocean. We show that crystal settling in a terrestrial magma ocean is crucially affected by latitude as well as by rotational strength and crystal density. Due to rotation an inhomogeneous accumulation of crystals during magma ocean solidification with a distinct crystal settling between pole and equator could occur. One could speculate that this may have potentially strong effects on the magma ocean solidification time and the early mantle composition. It could support the development of a basal magma ocean and the formation of anomalies at the core‐mantle boundary in the equatorial region, reaching back to the time of magma ocean solidification.

Magma chamber

Settling

10.1002/2015jb012053

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Citations (20)

Depletion of a brine layer at the base of ridge-crest hydrothermal systems

Earth and Planetary Science Letters (2000)

Stan Schoofs Ulrich Hansen

Brine

Convective mixing

10.1016/s0012-821x(00)00184-9

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