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Thermal evolution of a differentiated Ganymede and implications for surface features Thermal evolution of a differentiated Ganymede and implications for surface features

Thermal evolution models are presented for Ganymede, assuming a mostly differentiated initial state of a water ocean overlying a rock layer. The only heat sources are assumed to be primordial heat (provided by accretion) and the long-lived radiogenic heat sources in the rock component. As Ganymede cools, the ocean thins, and two ice layers develop, one above composed of ice I, and the...
Authors
Randolph L. Kirk, David J. Stevenson

Hydromagnetic constraints on deep zonal flows in the giant planets Hydromagnetic constraints on deep zonal flows in the giant planets

The observed zonal flows of the giant planets will, if they penetrate below the visible atmosphere, interact significantly with the planetary magnetic field outside the metallized core. The appropriate measure of this interaction is the Chandrasekhar number Q = H^2 /4πρνα^2 λ (H = radial component of the magnetic field, ν = eddy viscosity, λ = magnetic diffusivity, α^-1 = length scale on...
Authors
Randolph L. Kirk, David J. Stevenson

Passive margins: U.S. Geological Survey Line 19 across the Georges Bank basin Passive margins: U.S. Geological Survey Line 19 across the Georges Bank basin

Georges Bank is a shallow part of the Atlantic continental shelf southeast of New England (Emery and Uchupi, 1972, 1984). This bank, however, is merely the upper surface of several sedimentary basins overlying a block-faulted basement of igneous and metamorphic crystalline rock. Sedimentary rock forms a seaward-thickening cover that has accumulated in one main depocenter and several...
Authors
Kim D. Klitgord, John S. Schlee, John A. Grow

Some effects of quiet geomagnetic field changes upon values used for main field modeling Some effects of quiet geomagnetic field changes upon values used for main field modeling

The effects of three methods of data selection upon the assumed main field levels for geomagnetic observatory records used in main field modeling were investigated for a year of very low solar-terrestrial activity. The first method concerned the differences between the year's average of quiet day field values and the average of all values during the year. For H these differences were 2-3...
Authors
W.H. Campbell
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