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| Titel |
A study of magnetic fluctuations and their anomalous scaling in the solar wind: the Ulysses fast-latitude scan |
| VerfasserIn |
C. Pagel, A. Balogh |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 8, no. 4/5 ; Nr. 8, no. 4/5, S.313-330 |
| Datensatznummer |
250005302
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| Publikation (Nr.) |
 copernicus.org/npg-8-313-2001.pdf |
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| Zusammenfassung |
| The solar wind is a
highly turbulent and intermittent medium at frequencies between 10-4 and
10-1 Hz. Power spectra are used to look at fluctuations in the
components of the magnetic field at high frequencies over a wide range of
latitudes. Results show steady turbulence in the polar regions of the Sun
and a more varied environment in the equatorial region. The magnetic field
fluctuations exhibit anomalous scaling at high frequencies. Various models
have been proposed in an attempt to better understand the scaling nature
of such fluctuations in neutral fluid turbulence. We have used the Ulysses
fast latitude scan data to perform a wide ranging comparison of three such
models on the solar wind magnetic field data: the well-known P model, in
both its Kolmogorov and Kraichnan forms, the lognormal cascade model and a
model adapted from atmospheric physics, the G infinity model. They were
tested by using fits to graphs of the structure function exponents g(q),
by making a comparison with a non-linear measure of the deviation of g(q)
from the non-intermittent straight line, and by using extended self
similarity technique, over a large range of helio-latitudes. Tests of all
three models indicated a high level of intermittency in the fast solar
wind, and showed a varied structure in the slow wind, with regions of
apparently little intermittency next to regions of high intermittency,
implying that the slow wind has no uniform origin. All but one of the
models performed well, with the lognormal and Kolmogorov P model
performing the best over all the tests, indicating that inhomogeneous
energy transfer in the cascade is a good description. The Kraichnan model
performed relatively poorly, and the overall results show that the
Kraichnan model of turbulence is not well supported over the frequency and
distance ranges of our data set. The G infinity model fitted the results
surprisingly well and showed that there may very well be important
universal geometrical aspects of intermittency over many physical systems. |
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