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The magnetic fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly (1-4) (the slowly rotating Sun generates its field through a different dynamo mechanisms (5)). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear (5,6). Here we report an extension of a scaling law derived from geodynamo models (7)to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy flux available for generating the magnetic field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable., So far, attempts to explain the magnetic field strength of natural dynamos have been largely heuristic and disparate for planets and stars. The field strength in a planetary dynamo is [...]

Author(s): Ulrich R. Christensen (corresponding author) [1] Mercury has a global magnetic field of internal origin and it is thought that a dynamo operating in the fluid part of Mercury's [...]

Author(s): Ulrich R. Christensen (corresponding author) [1]; Andreas Tilgner [2] In the Earth's fluid outer core, a dynamo process converts thermal and gravitational energy into magnetic energy. The power needed [...]

A three-dimensional convection model incorporating an endothermic phase transition close to the core-mantle boundary is used to analyze the convective evolution of the martian mantle. The results show the development of a single-plume pattern of convection on Mars consistent with the volcanic distribution, gravity field shape and the gross tectonic stress pattern of the planet. Thermal convection in the martian mantle is unlike that in the Earth. A single large upswelling region exists beneath the Tharsis region of Mars.

Earth's magnetic field is often depicted as though a gigantic bar magnet resides inside our planet. In fact, the magnetic field is created by strong electrical currents generated by a [...]

Volcanic hotspots were thought to be fixed points thjat could be used as reference frames for tectonic plates, but they have proved to be more mobile than expected. Seismic tomography results have shown that volcanic plumes cannot rise through immobile groundwork. Steinberger and O'Connell have assessed Haiwaiian hotspots. Tarduno and Cottrell have shown that research into magnetization of volcanic material is one way to assess hotspot migration and separate it from plate drift.

Geophysical models indicate that convection can cause compositional layers to form in the Earth's mantle. Furthermore, S. Weinstein's numerical models show that the seismic discontinuity 660 kilometers down functions as a chemical filter that separates buoyant rock from dense rock. Hence the seismic discontinuity, defined as a region where density goes up by 10% in a space of a few kilometers, generates a phase change that in turn gives rise to layers.