000003627 001__ 3627
000003627 005__ 20181005175717.0
000003627 037__ $$aCTALK-2018-0084
000003627 100__ $$aShestov, Sergei
000003627 245__ $$aInitiation of Alfvenic turbulence by Alfven wave collisions: a numerical study
000003627 260__ $$c2018
000003627 269__ $$c2018-06-21
000003627 520__ $$aRecent studies have revealed that the turbulence in magnetized plasmas is greatly affected by the Alfvén effect. The well-documented example is the solar-wind turbulence whose nature is essentially Alfvénic and turbulent fluctuations can be approximately described as Alfvén waves (AWs). We study using numerical MHD approach the commonly accepted presumption that the AW turbulence is generated by the collisions between counter-propagating AWs in the conditions typical for the solar wind. To this end, we launch in the simulation box two counterpropagating AWs and follow their evolution observing how the wave profiles are distorted during their collision. The initial waves are linearly polarized in two orthogonal planes, their cross-field amplitude profiles vary normally to their polarization planes, and their magnetic amplitudes are about 0.1 of the mean magnetic field. Polarization and spectral properties of the perturbations generated after a single collision between such AWs were analyzed in detail. We found that the perturbations had smaller-scale across the mean magnetic field compared to the original waves, and the perturbations had different polarizations. The obtained results confirm theoretical predictions that progressively larger cross-field wavenumbers are generated by the AW collisions. However, the observed amplitudes of the perturbations (1-2% of the original AW amplitudes) are not sufficient to generate the spectral transport typical for the strong turbulence proposed by Goldreich & Sridhar (1995). Instead, the obtained spectral transport implies conditions typical for the weak turbulence where many collisions are needed to generate a single cascade step. Further simulations are underway in an attempt to figure out if a single-step cascade can be generated by two counter-propagating AWs.
000003627 536__ $$a3PRODPROBA3/$$c3PRODPROBA3/$$f3PRODPROBA3
000003627 594__ $$aSTCE
000003627 6531_ $$aturbulence, MHD, numerical simulations
000003627 700__ $$aVoitenko, Yuri
000003627 700__ $$aZhukov, Andrei
000003627 773__ $$tSolar Wind XV
000003627 8560_ $$fsergei.shestov@observatoire.be
000003627 85642 $$ahttps://www.conftool.pro/solarwind2018/sessions.php
000003627 906__ $$aContributed
000003627 980__ $$aCTALKCONT