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| Titel |
Spectral properties of electromagnetic turbulence in plasmas |
| VerfasserIn |
D. Shaikh, P. K. Shukla |
| 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 ; 16, no. 2 ; Nr. 16, no. 2 (2009-03-12), S.189-196 |
| Datensatznummer |
250013130
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| Publikation (Nr.) |
 copernicus.org/npg-16-189-2009.pdf |
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| Zusammenfassung |
| We report on the nonlinear turbulent processes associated with
electromagnetic waves in plasmas. We focus on low-frequency (in
comparison with the electron gyrofrequency) nonlinearly interacting
electron whistlers and nonlinearly interacting Hall-magnetohydrodynamic
(H-MHD) fluctuations in a magnetized plasma.
Nonlinear whistler mode turbulence study in a magnetized plasma
involves incompressible electrons and immobile ions. Two-dimensional
turbulent interactions and subsequent energy cascades are critically
influenced by the electron whisters that behave distinctly for
scales smaller and larger than the electron skin depth. It is found
that in whistler mode turbulence there results a dual cascade
primarily due to the forward spectral migration of energy that
coexists with a backward spectral transfer of mean squared magnetic
potential. Finally, inclusion of the ion dynamics, resulting from a
two fluid description of the H-MHD plasma, leads to several
interesting results that are typically observed in the solar wind
plasma. Particularly in the solar wind, the high-time-resolution
databases identify a spectral break at the end of the MHD inertial range
spectrum that corresponds to a high-frequency regime. In the latter,
turbulent cascades cannot be explained by the usual MHD model and a
finite frequency effect (in comparison with the ion gyrofrequency) arising
from the ion inertia is essentially included to discern the dynamics of the
smaller length scales (in comparison with the ion skin depth). This leads
to a nonlinear H-MHD model, which is presented in this paper. With the help of
our 3-D H-MHD code, we find that the characteristic turbulent interactions in
the high-frequency regime evolve typically on kinetic-Alfvén time-scales. The turbulent
fluctuation associated with kinetic-Alfvén interactions are
compressive and anisotropic and possess equipartition of the kinetic
and magnetic energies. |
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