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| Titel |
Large-scale velocity fluctuations in polar solar wind |
| VerfasserIn |
B. Bavassano, R. Bruno, R. D'Amicis |
| 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 ; 23, no. 3 ; Nr. 23, no. 3 (2005-03-30), S.1025-1031 |
| Datensatznummer |
250015199
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1025-2005.pdf |
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| Zusammenfassung |
| The 3-D structure of the solar wind varies dramatically along
the Sun's activity cycle. In the present paper we focus on some properties of
the polar solar wind. This is a fast, teneous, and steady flow (as compared
to low-latitude conditions) that fills the high-latitude heliosphere at low
solar activity. The polar wind has been extensively investigated by Ulysses,
the first spacecraft to perform in-situ measurements in the high-latitude
heliosphere. Though the polar wind is quite a uniform flow, fluctuations in
its velocity do not appear negligible. A simple way to characterize the solar
wind structure is that of performing a multi-scale statistical analysis of
the wind velocity differences. The occurrence frequency distributions of
velocity differences at time lags from 1 to 1024h and the corresponding
values of mean, standard deviation, skewness, and kurtosis have been
obtained. A comparison with previous results in ecliptic wind at both low and
high solar activity has been performed. It comes out that the kind of trend
observed in the distributions for changing scale is the same for the
different solar wind regimes. Differences between different flows just have
an effect on the values of the distribution moments and the scales at which
the transition from non-Gaussian to Gaussian-like behaviours occurs. This is
typical of systems in which random fluctuations are mixed to coherent
structures of some characteristic size, in other words, systems where
long-range correlations cannot be neglected. |
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