Journal
PHYSICS OF THE EARTH AND PLANETARY INTERIORS
Volume 135, Issue 2-3, Pages 125-134Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/S0031-9201(02)00211-X
Keywords
geomagnetic field spectra; secular variation; persistence times
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Many natural phenomena show a relationship between their spatial and temporal Fourier spectra. This paper discusses such a connection for the geomagnetic field, when some assumptions are made about the (exponential or power-law) behaviour of the spatial power spectrum of the field itself and that of its time derivative (the spatial spectrum of the secular variation) as estimated from global geomagnetic field models. It is shown that, under either assumption, the temporal spectrum of the geomagnetic field computed at the core-mantle boundary (CMB) would have a power-law behaviour with a negative spectral exponent of about 0.5. At the Earth's surface, although the temporal spectrum obtained from the power-law spatial model assumes a slightly more complicated form, it can be practically approximated with a power law with a negative exponent of about 3.6. Analysis of magnetic observatory data confirms these results and that the starting hypotheses are reasonable, especially in view of the possibly chaotic state of the dynamical processes underlying the generation and maintenance of the geomagnetic field. (C) 2002 Elsevier Science B.V. All rights reserved.
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