Spatiotemporal response of a conducting sphere under simulated geomagnetic storm conditions
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abstract
A theoretical study of satellite-based geomagnetic induction signals from uniform and heterogeneous spheres is undertaken using existing analytic and semi-analytic harmonic solutions. Transient responses to ring current excitations are computed using inverse Fourier and Laplace methods. A wide range of simulated storm excitations from impulse to step-on are considered. The early-time radial and late-time polar responses are diagnostic of the electrical conductivity of the sphere. The early-time diagnostic is likely more useful because of better signal to noise characteristics. Induction signals from deeply buried heterogeneities are likely to be contained in the late-time responses and their extraction will require new statistical approaches that average over many storms and incorporate multi-satellite and ground-based observations. The spatiotemporal induction response shows an interesting crossover during which time the rapidly-evolving polar component starts to decays while the slowly-evolving radial component continues to grow. At the crossover time, the intensity of the field is independent of colatitude, an effect which could be sought in satellite induction data. 2003 Elsevier B.V. All rights reserved.
