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| Titel |
Non-Gaussian probability distributions of solar wind fluctuations |
| VerfasserIn |
E. Marsch, C. Y. Tu |
| 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 ; 12, no. 12 ; Nr. 12, no. 12, S.1127-1138 |
| Datensatznummer |
250011243
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| Publikation (Nr.) |
 copernicus.org/angeo-12-1127-1994.pdf |
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| Zusammenfassung |
| The probability distributions of field
differences ∆x(τ)=x(t+τ)-x(t),
where the variable x(t) may denote any solar wind scalar field or
vector field component at time t, have been calculated from time series
of Helios data obtained in 1976 at heliocentric distances near 0.3 AU. It is
found that for comparatively long time lag τ, ranging from a few hours
to 1 day, the differences are normally distributed according to a Gaussian. For
shorter time lags, of less than ten minutes, significant changes in shape are
observed. The distributions are often spikier and narrower than the equivalent
Gaussian distribution with the same standard deviation, and they are enhanced
for large, reduced for intermediate and enhanced for very small values of
∆x. This result is in accordance with fluid observations and
numerical simulations. Hence statistical properties are dominated at small scale
τ by large fluctuation amplitudes that are sparsely distributed, which
is direct evidence for spatial intermittency of the fluctuations. This is in
agreement with results from earlier analyses of the structure functions of
∆x. The non-Gaussian features are differently developed for
the various types of fluctuations. The relevance of these observations to the
interpretation and understanding of the nature of solar wind magnetohydrodynamic
(MHD) turbulence is pointed out, and contact is made with existing theoretical
concepts of intermittency in fluid turbulence. |
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