000003628 001__ 3628
000003628 005__ 20181005180023.0
000003628 037__ $$aCTALK-2018-0085
000003628 100__ $$aShestov, Sergei
000003628 245__ $$aInitiation of Alfvénic turbulence by Alfvén wave collissions: a numerical study
000003628 260__ $$c2018
000003628 269__ $$c2018-09-03
000003628 520__ $$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 AW. We set up a simulation box with equilibrium conditions, launch two counter-propagating Aws from the opposite boundaries, 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.
000003628 536__ $$a3PRODPROBA3/$$c3PRODPROBA3/$$f3PRODPROBA3
000003628 594__ $$aSTCE
000003628 6531_ $$aturbulence, MHD, numerical simulations, plasma turbulence
000003628 700__ $$aVoitenko, Yuri
000003628 700__ $$aZhukov, Andrei
000003628 773__ $$tBUKS 2018 Workshop, Tenerife, Spain
000003628 8560_ $$fsergei.shestov@observatoire.be
000003628 85642 $$ahttp://www.iac.es/congreso/BUKS2018/
000003628 906__ $$aContributed
000003628 980__ $$aCTALKCONT