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| Titel |
Turbulence in nearly incompressible fluids: density spectrum, flows, correlations and implication to the interstellar medium |
| VerfasserIn |
S. Dastgeer, G. P. Zank |
| 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 ; 12, no. 1 ; Nr. 12, no. 1 (2005-01-28), S.139-148 |
| Datensatznummer |
250010387
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| Publikation (Nr.) |
 copernicus.org/npg-12-139-2005.pdf |
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| Zusammenfassung |
| Interstellar scintillation and angular radio wave broadening
measurements show that interstellar and solar wind (electron) density
fluctuations exhibit a Kolmogorov-like k-5/3 power spectrum
extending over many decades in wavenumber space. The ubiquity of the
Kolmogorov-like interstellar medium (ISM) density spectrum led to an
explanation based on coupling incompressible magnetohydrodynamic (MHD)
fluctuations to density fluctuations through a "pseudosound"
relation within the context of "nearly incompressible" (NI)
hydrodynamics (HD) and MHD models. The NI theory provides a
fundamentally different explanation for the observed ISM density
spectrum in that the density fluctuations can be a consequence of
passive scalar convection due to background incompressible
fluctuations. The theory further predicts generation of long-scale
structures and various correlations between the density, temperature
and the (magneto) acoustic as well as convective pressure fluctuations
in the compressible ISM fluids in different thermal regimes that are
determined purely by the thermal fluctuation level. In this paper, we
present the results of our two dimensional nonlinear fluid
simulations, exploring various nonlinear aspects that lead to inertial
range ISM turbulence within the context of a NI hydrodymanics
model. In qualitative agreement with the NI predictions and the
in-situ observations, we find that i) the density fluctuations exhibit
a Kolmogorov-like spectrum via a passive convection in the field of
the background incompressible fluctuations, ii) the compressible ISM
fluctuations form long scale flows and structures, and iii) the
density and the temperature fluctuations are anti-correlated. |
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