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| Titel |
Intermittency, non-Gaussian statistics and fractal scaling of MHD fluctuations in the solar wind |
| VerfasserIn |
E. Marsch, C.-Y. Tu |
| 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 ; 4, no. 2 ; Nr. 4, no. 2, S.101-124 |
| Datensatznummer |
250001576
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| Publikation (Nr.) |
 copernicus.org/npg-4-101-1997.pdf |
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| Zusammenfassung |
| This paper gives a review of some recent work on intermittency,
non-Gaussian statistics, and fractal scaling of solar wind magnetohydrodynamic
turbulence. Model calculations and theories are discussed and put in their
context with the in-situ observations of the solar wind fluctuations, essentially
of the flow velocity and magnetic field. Emphasis is placed more on a comparison
of the data with the theory than on a complete derivation of the model
results, which are treated in a more tutorial fashion. The introduction
reminds of some important observations and key aspects of the solar wind
turbulence. Then structure functions are defined and observational results
discussed. The probability density functions provide a direct means to
analyse the statistical properties of the fluctuations. Evidence for non-Gaussian
statistics is provided. Intermittency and simple scaling models are discussed,
which yield algebraic expressions for the scaling exponents of the structure
functions. The concept of the extended self-similarity is presented and
corresponding observational evidence for its existence in the solar wind
is provided. Subsequently, and extended structure function model, including
the p-model scaling and a scale-dependent cascade, is discussed and compared
with selected measurements. The basics of the multifractals are presented
and applied to solar wind data. The multifractal scaling of the kinetic
energy flux as proxy for the unknown cascading rate is established observationally,
and the so-called multifractal spectrum is obtained. Finally, the scaling
exponents of the associated correlation functions are derived and analysed.
The paper concludes with a discussion of the empirical results and prospects
for the future research in this field and in solar wind MHD turbulence
in general. |
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