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Titel |
On multifractality of high-latitude geomagnetic fluctuations |
VerfasserIn |
Z. Vörös |
Medientyp |
Artikel
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Sprache |
Englisch
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ISSN |
0992-7689
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Digitales Dokument |
URL |
Erschienen |
In: Annales Geophysicae ; 18, no. 10 ; Nr. 18, no. 10, S.1273-1282 |
Datensatznummer |
250014077
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Publikation (Nr.) |
copernicus.org/angeo-18-1273-2000.pdf |
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Zusammenfassung |
In order to contribute to the understanding
of solar wind-magnetosphere interactions the multifractal scaling properties of
high-latitude geomagnetic fluctuations observed at the Thule observatory have
been studied. Using the local observatory data and the present experimental
knowledge only it seems hard to characterize directly the, presumably
intermittent, mesoscale energy accumulation and dissipation processes taking
place at the magnetotail, auroral region, etc. Instead a positive probability
measure, describing the accumulated local geomagnetic signal energy content at
the given time scales has been introduced and its scaling properties have been
studied. There is evidence for the multifractal nature of the so defined
intermittent field ε, a result obtained by using the recently
introduced technique of large deviation multifractal spectra. This technique
allows us to describe the geomagnetic fluctuations locally in time by means of
singularity exponents α, which represent a generalization of the
local degree of differentiability and characterize the power-law scaling
dependence of the introduced measure on resolution. A global description of the
geomagnetic fluctuations is insured by the spectrum of exponents f(α)
which represents a rate function quantifying the deviations of the observed
singularities α from the expected value. The results show that there
exists a multifractal counterpart of the previously reported spectral break and
different types of f(α) spectra describe the fluctuations in
direct dissipation or loading-unloading regimes of the solar wind-magnetosphere
interaction. On the time scale of substorms and storms the multi-fractal
structure of the loading-unloading mode fluctuations seems to be analogous to
the simple multiplicative P-model, while the f(α) spectra in
direct dissipation regime are close but not equal to the features of a uniform
distribution. Larger deviations from the multiplicative model are observed when
the influence of the solar wind fluctuations is examined. On this basis it is
expected that an extended multifractal analysis of the singularity structure of
near-Earth plasma system fluctuations would lead to improved geomagnetic
diagnosis of the magnetospheric dynamics.
Key words: Magnetospheric physics
(magnetosphere-ionosphere interaction; solar wind-magnetosphere interactions;
storms and substorms) |
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