Shestov, S ; Voitenko, Y ; Zhukov, A

Talk presented at Fifth Uk-Ukraine-Spain meeting on Solar Physics and Space Sciences on 2019-08-29

Abstract: According to the recent theory of Alfvénic turbulence, the turbulent cascade generated by Alfvén-wave collisions proceeds along the critically balanced path in the wavenumber space, where the linear propagation time of Alfvén waves adjusts to their nonlinear interaction time. We study numerically elementary Alfvén-wave collisions and demonstrate that, contrary to theoretical expectations, the critically balanced collisions provide a relatively weak spectral transport insufficient to generate strong Alfvénic turbulence. We also show that the strong turbulence can be generated by the collisions of Alfvén waves with perpendicular wavelengths shifted to shorter scales as compared to the critically-balanced path. The spectral transport in both cases generates perturbations with perpendicular (to the mean magnetic field) scales smaller than in the original waves and with different polarization, which qualitatively agrees with theoretical predictions. We discuss effects that can suppress the critically-balanced collisions and related consequences for the turbulent plasma heating in the solar coronal loops and solar wind.

Keyword(s): Turbulence ; Alfven waves ; MHD
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Funding: 3PRODPROBA3/3PRODPROBA3/3PRODPROBA3