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| Titel |
Temporal intermittency of Alfvenic turbulence dissipation: effect of intermediate shock instabilities |
| VerfasserIn |
P.-L. Sulem, T. Passot, D. Laveder |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250061381
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| Zusammenfassung |
| We present numerical simulations of the turbulent regime that establishes when a random
driving is supplemented to the Cohen-Kulsrud equation for non-dispersive Alfvén waves.
This equation appears as a paradigm for systems that, like the primitive MHD equations, are
non strictly hyperbolic. In this case, Rankine-Hugoniot conditions do not uniquely specify
the shock dynamics, and zero-viscosity limit is not necessarity well defined. This
situation leads to the possibility of intermediate shocks corresponding to simultaneous
jumps of the amplitude and of the direction of the magnetic field. Such structures
are unstable when the phase variation exceeds 180°. The front steepens and the
amplitude jump increases up to the formation of a neutral point for the transverse
magnetic field, an effect leading to a change in the wave polarization. A fast shock is
simultaneously emitted, and the intermediate shock relaxes to a stable state with an
angular jump smaller than 180°. Such a process leads to short and intense dissipation
peaks with a power-law distribution. This strongly affects the dynamics which turns
out to be significantly different from both Kolmogorov and Burgers turbulence
phenomenologies. |
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