Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence
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Authors
Voitenko, Y.
De Keyser, J.
Discipline
Physical sciences
Subject
amplitude
coupling
dissipation
magnetohydrodynamics
threshold
turbulence
Audience
Scientific
Date
2011Metadata
Show full item recordDescription
A weakly dispersive range (WDR) of kinetic Alfvén turbulence is identified and investigated for the first time in the context of the MHD/kinetic turbulence transition. We find perpendicular wavenumber spectra ∝ k⊥−3 and ∝ k⊥−4 formed in WDR by strong and weak turbulence of kinetic Alfvén waves (KAWs), respectively. These steep WDR spectra connect shallower spectra in the MHD and strongly dispersive KAW ranges, which results in a specific double-kink (2-k) pattern often seen in observed turbulent spectra. The first kink occurs where MHD turbulence transforms into weakly dispersive KAW turbulence; the second one is between weakly and strongly dispersive KAW ranges. Our analysis suggests that partial turbulence dissipation due to amplitude-dependent non-adiabatic ion heating may occur in the vicinity of the first spectral kink. The threshold-like nature of this process results in a conditional selective dissipation that affects only the largest over-threshold amplitudes and that decreases the intermittency in the range below the first spectral kink. Several recent counter-intuitive observational findings can be explained by the coupling between such a selective dissipation and the nonlinear interaction among weakly dispersive KAWs.
Citation
Voitenko, Y.; De Keyser, J. (2011). Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence. , Nonlinear Processes in Geophysics, Vol. 18, Issue 5, 587-597, DOI: 10.5194/npg-18-587-2011.Identifiers
scopus: 2-s2.0-80052722919
Type
Article
Peer-Review
Yes
Language
eng