2014/04/25 by W. H. Matthaeus, S. Oughton, K. T. Osman +8
Physics and Astronomy · #Cascade #Gyrokinetics #Ionosphere and magnetosphere dynamics #Kinetic energy #Magnetic confinement fusion research #Magnetohydrodynamic drive #Magnetohydrodynamic turbulence #Nonlinear system #Scale (ratio) #Solar and Space Plasma Dynamics #Solar wind #Turbulence #physics.plasm-ph #physics.space-ph
paper · pdf · doi:10.1088/0004-637x/790/2/155
9 pages, 4 figures, submitted to the Astrophysical Journal
arxiv created 2014/04/25 · openalex publication_date 2014/07/17 · arxiv updated 2015/06/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The application of linear kinetic treatments to plasma waves, damping, and instability requires favorable inequalities between the associated linear timescales and timescales for nonlinear (e.g., turbulence) evolution. In the solar wind these two types of timescales may be directly compared using standard Kolmogorov-style analysis and observational data. The estimated local (in scale) nonlinear magnetohydrodynamic cascade times, evaluated as relevant kinetic scales are approached, remain slower than the cyclotron period, but comparable to or faster than the typical timescales of instabilities, anisotropic waves, and wave damping. The variation with length scale of the turbulence timescales is supported by observations and simulations. On this basis the use of linear theory—which assumes constant parameters to calculate the associated kinetic rates—may be questioned. It is suggested that the product of proton gyrofrequency and nonlinear time at the ion gyroscales provides a simple measure of turbulence influence on proton kinetic behavior.