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Analysis of the geomagnetic activity of the D(st) index and self-affine fractals using wavelet transforms

Wei, H.L., Billings, S.A. and Balikhin, M. (2004) Analysis of the geomagnetic activity of the D(st) index and self-affine fractals using wavelet transforms. Nonlinear Processes in Geophysics, 11 (3). pp. 303-312. ISSN 1607-7946


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The geomagnetic activity of the D(st) index is analyzed using wavelet transforms and it is shown that the D(st) index possesses properties associated with self-affine fractals. For example, the power spectral density obeys a power-law dependence on frequency, and therefore the D(st) index can be viewed as a self-affine fractal dynamic process. In fact, the behaviour of the D(st) index, with a Hurst exponent H≈0.5 (power-law exponent β≈2) at high frequency, is similar to that of Brownian motion. Therefore, the dynamical invariants of the D(st) index may be described by a potential Brownian motion model. Characterization of the geomagnetic activity has been studied by analysing the geomagnetic field using a wavelet covariance technique. The wavelet covariance exponent provides a direct effective measure of the strength of persistence of the D(st) index. One of the advantages of wavelet analysis is that many inherent problems encountered in Fourier transform methods, such as windowing and detrending, are not necessary.

Item Type: Article
Copyright, Publisher and Additional Information: © Author(s) 2004. This work is licensed under a Creative Commons Attribution, NonCommercial and ShareAlike Licence.
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Automatic Control and Systems Engineering (Sheffield)
Depositing User: Repository Officer
Date Deposited: 06 Feb 2007
Last Modified: 05 Jun 2014 14:14
Published Version: http://www.nonlin-processes-geophys.net/11/303/200...
Status: Published
Publisher: Copernicus GmbH on behalf of the European Geosciences Union (EGU) and the American Geophysical Union (AGU)
Refereed: Yes
URI: http://eprints.whiterose.ac.uk/id/eprint/1946

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