2016/02/11 by Munehito Shoda, T. Yokoyama, Takaaki Yokoyama
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Circular polarization #Computational physics #Cross-polarized wave generation #Geomagnetism and Paleomagnetism Studies #Ionosphere and magnetosphere dynamics #Linear polarization #Nonlinear system #Optics #Physics #Plasma #Polarization (electrochemistry) #Quantum mechanics #Reflection (computer programming) #Solar and Space Plasma Dynamics #Solar wind #astro-ph.SR
paper · pdf · doi:10.3847/0004-637x/820/2/123
31 pages, 12 figures, accepted by The Astrophysical Journal
arxiv created 2016/02/11 · openalex publication_date 2016/03/30 · arxiv updated 2016/04/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
ABSTRACT Using one-dimensional numerical simulations, we study the elementary process of Alfvén wave reflection in a uniform medium, including nonlinear effects. In the linear regime, Alfvén wave reflection is triggered only by the inhomogeneity of the medium, whereas in the nonlinear regime, it can occur via nonlinear wave–wave interactions. Such nonlinear reflection (backscattering) is typified by decay instability. In most studies of decay instabilities, the initial condition has been a circularly polarized Alfvén wave. In this study we consider a linearly polarized Alfvén wave, which drives density fluctuations by its magnetic pressure force. For generality, we also assume a broadband wave with a red-noise spectrum. In the data analysis, we decompose the fluctuations into characteristic variables using local eigenvectors, thus revealing the behaviors of the individual modes. Different from the circular-polarization case, we find that the wave steepening produces a new energy channel from the parent Alfvén wave to the backscattered one. Such nonlinear reflection explains the observed increasing energy ratio of the sunward to the anti-sunward Alfvénic fluctuations in the solar wind with distance against the dynamical alignment effect.