Nonlinear and Linear Timescales near Kinetic Scales in Solar Wind Turbulence
Abstract
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 Kolmogorovstyle 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.
 Publication:

The Astrophysical Journal
 Pub Date:
 August 2014
 DOI:
 10.1088/0004637X/790/2/155
 arXiv:
 arXiv:1404.6569
 Bibcode:
 2014ApJ...790..155M
 Keywords:

 magnetohydrodynamics: MHD;
 solar wind;
 Sun: corona;
 turbulence;
 Physics  Space Physics;
 Physics  Plasma Physics
 EPrint:
 9 pages, 4 figures, submitted to the Astrophysical Journal