 |
| Titel |
Evolution of Multiscale Multifractal Turbulence in the Heliosphere |
| VerfasserIn |
W. M. Macek, A. Wawrzaszek |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021898
|
|
|
|
|
|
| Zusammenfassung |
| The aim of this study is to examine the question of scaling properties of intermittent
turbulence in the space environment. We analyze time series of velocities of the slow
and fast speed streams of the solar wind measured in situ by Helios 2, Advanced
Composition Explorer and Voyager 2 spacecraft in the inner and outer heliosphere
during solar minimum and maximum at various distances from the Sun. To quantify
asymmetric scaling of solar wind turbulence, we consider a generalized two-scale
weighted Cantor set with two different scales describing nonuniform distribution of the
kinetic energy flux between cascading eddies of various sizes. We investigate the
resulting spectrum of generalized dimensions and the corresponding multifractal
singularity spectrum depending on one probability measure parameter and two rescaling
parameters, demonstrating that the multifractal scaling is often rather asymmetric.
In particular, we show that the degree of multifractality for the solar wind during
solar minimum is greater for fast streams velocity fluctuations than that for the
slow streams; the fast wind during solar minimum may exhibit strong asymmetric
scaling. Moreover, we observe the evolution of multifractal scaling of the solar wind
in the outer heliosphere. It is worth noting that for the model with two different
scaling parameters a much better agreement with the solar wind data is obtained,
especially for the negative index of the generalized dimensions. Therefore we argue that
there is a need to use a two-scale cascade model. Hence we propose this new more
general model as a useful tool for analysis of intermittent turbulence in various
environments.
References
[1] W. M. Macek and A. Szczepaniak, Generalized two-scale weighted Cantor
set model for solar wind turbulence, Geophys. Res. Lett., 35, L02108,
doi:10.1029/2007GL032263 (2008).
[2] A. Szczepaniak and W. M. Macek, Asymmetric multifractal model for solar
wind intermittent turbulence, Nonlin. Processes Geophys., 15, 615–620 (2008),
http://www.nonlin-processes-geophys.net/15/615/2008/.
[3] W. M. Macek and A. Wawrzaszek, Evolution of asymmetric multifractal
scaling of solar wind turbulence in the outer heliosphere, J. Geophys. Res.,
A013795, doi:10.1029/2008JA013795, in press. |
|
|
|
|
|
|