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| Titel |
Velocity fluctuations in polar solar wind: a comparison between different solar cycles |
| 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 ; 27, no. 2 ; Nr. 27, no. 2 (2009-02-20), S.877-883 |
| Datensatznummer |
250016422
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| Publikation (Nr.) |
 copernicus.org/angeo-27-877-2009.pdf |
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| Zusammenfassung |
| The polar solar wind is a fast, tenuous and steady flow that, with the
exception of a relatively short phase around the Sun's activity maximum,
fills the high-latitude heliosphere. The polar wind properties have been
extensively investigated by Ulysses, the first spacecraft able to perform
in-situ measurements in the high-latitude heliosphere. The out-of-ecliptic
phases of Ulysses cover about seventeen years. This makes possible to study
heliospheric properties at high latitudes in different solar cycles. In the
present investigation we focus on hourly- to daily-scale fluctuations of the
polar wind velocity. Though the polar wind is a quite uniform flow,
fluctuations in its velocity do not appear negligible. A simple way to
characterize wind velocity variations is that of performing a multi-scale
statistical analysis of the wind velocity differences. Our analysis is based
on the computation of velocity differences at different time lags and the
evaluation of statistical quantities (mean, standard deviation, skewness, and
kurtosis) for the different ensembles. The results clearly show that, though
differences exist in the three-dimensional structure of the heliosphere
between the investigated solar cycles, the velocity fluctuations in the core
of polar coronal holes exhibit essentially unchanged statistical properties. |
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