Numerical simulations of geomagnetic short-timescale variations

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I performed numerical simulations of convection and geomagnetic field generation processes in Earth's liquid metallic core to reproduce several characteristic geomagnetic secular variations. The numerical result exhibits torsional oscillations that are composed of traveling waves toward and out of the Earth's rotation axis, suggesting that they are created by turbulence in internal core convection. The result also shows clear westward drift in the core-surface magnetic field particularly in high-wavenumber components and in the low latitudes, and I pointed out existence of dispersion in the westward drift. In order to figure out this dispersion property, I conducted linear stability analysis of axisymmetric magnetic field in an inviscid rotating fluid sphere, and discussed possible relations between westward propagation of slow hydromagnetic wave and the geomagnetic westward drift.