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- Ulli Christensen, Peter L. Olson, A. Glatzmaier
- 1999

We analyse *50 3-D numerical calculations of hydrodynamic dynamos driven by convection in a spherical shell. We examine rigid and stress-free boundaries, with Prandtl number 1, magnetic Prandtl numbers in the range 0.5^5, Ekman numbers E~10{3^10{4 and Rayleigh numbers to 15 times critical. No parametrizations such as hyperviscosities are used. Successfulâ€¦ (More)

- J M Aurnou, Steven Andreadis, Lixin Zhu, Peter L. Olson
- 2002

Results of thermal convection experiments in a rotating uid with a geometry similar to the Earth's core tangent cylinder are presented. We nd four di erent regimes of convection. In order of increasing heat ow, these are: (1) subcritical (no convection), (2) helical plumes (hetons) around the tangent cylinder, (3) hetons throughout the tangent cylinder, andâ€¦ (More)

Scaling laws are derived for the time-average magnetic dipole moment in rotating convection-driven numerical dynamo models. Results from 145 dynamo models with a variety of boundary conditions and heating modes, covering a wide section of parameter space, show that the time-average dipole moment depends on the convective buoyancy flux F. Two distinctâ€¦ (More)

The four most recent large mass extinction events in the Phanerozoic â€“ the Cretaceousâ€“Tertiary (KT), the Triassicâ€“Jurassic (TJ), and the Permo-Triassic (PT) and Guadalupianâ€“Tatarian (GT) doublet â€“ are associated with a major flood basalt eruption, with the timing of peak volcanic activity corresponding within measurement uncertainties to the extinctionâ€¦ (More)

- Peter L. Olson
- Proceedings of the National Academy of Sciencesâ€¦
- 2007

Self-sustaining numerical dynamos are used to infer the sources of low-frequency secular variation of the geomagnetic field. Gravitational dynamo models powered by compositional convection in an electrically conducting, rotating fluid shell exhibit several regimes of magnetic field behavior with an increasing Rayleigh number of the convection, includingâ€¦ (More)

- Julien Aubert, Hagay Amit, Gauthier Hulot, Peter L. Olson
- Nature
- 2008

Seismic waves sampling the top 100 km of the Earth's inner core reveal that the eastern hemisphere (40 degrees E-180 degrees E) is seismically faster, more isotropic and more attenuating than the western hemisphere. The origin of this hemispherical dichotomy is a challenging problem for our understanding of the Earth as a system of dynamically coupledâ€¦ (More)

- Peter L. Olson, Dayanthie S. Weeraratne
- Philosophical transactions. Series Aâ€¦
- 2008

Short-lived isotope systematics, mantle siderophile abundances and the power requirements of the geodynamo favour an early and high-temperature core-formation process, in which metals concentrate and partially equilibrate with silicates in a deep magma ocean before descending to the core. We report results of laboratory experiments on liquid metal dynamicsâ€¦ (More)

We present numerical dynamo models which qualitatively reproduce some structural characteristics of the present-day geomagnetic field. Timedependent convection in an electrically conducting, rotating spherical shell at Ekman numbers 1 3 x l0 -4 generates dipole-dominated magnetic fields, which exhibit distinct bundles of strong radial flux at highâ€¦ (More)

- Peter L. Olson, Hagay Amit
- Naturwissenschaften
- 2006

The dipole moment of Earthâ€™s magnetic field has decreased by nearly % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9%â€¦ (More)

[1] We investigate the direct thermal effects of giant impacts on the Martian core and its dynamo. Shock wave heating of Mars is calculated in terms of the impact velocity and the final basin size. Although much of the shock wave heat is deposited in the mantle, shock heating from a giant impact produces non-uniform temperatures in the core, leading to anâ€¦ (More)