Kinematic-gravity model of geodynamo

Emergent gravity requires kinematic nonlocality.

This Letter refines arguments forbidding nonlinear dynamical gravity from appearing in the low energy effective description of field theories with local kinematics, even for those with instantaneous long-range interactions. Specifically, we note that gravitational theories with universal coupling to energy-an intrinsically nonlinear phenomenon-are characterized by Hamiltonians that are pure bou...

Complex polarity reversals in a geodynamo model

A Grid-spectral Method of the Solution of the 3d Kinematic Geodynamo with the Inner Core

S u m m a r y : A 3D kinematic geodynamo model in a sphere with the conductive solid inner core is considered. The 3D magnetic field and velocity field are resolved in the physical space for rand 0-coordinates, whereas the sinand cos-decomposition is applied to the ^-coordinate. The additional boundary conditions for the case of non-zero velocity field on the boundaries of the liquid spherical ...

Simulating the geodynamo

Three-dimensional numerical simulations of convection and magnetic ®eld generation in the Earth’s core now span several hundred thousand years; the magnetic ®eld created during most of this time has an intensity, structure and time dependence similar to the present geomagnetic ®eld. Five models are described here. The ®rst is a homogeneous Boussinesq model, driven steadily by heat sources on th...

Geodynamo theory and simulations

80 years ago, Joseph Larmor planted the seed that grew into today’s imposing body of knowledge about how the Earth’s magnetic field is created. His simple idea, that the geomagnetic field is the result of dynamo action in the Earth’s electrically conducting, fluid core, encountered many difficulties, but these have by now been largely overcome, while alternative proposals have been found to be ...