Numerical simulation of kinetic Alfvén waves to study filament formation and their nonlinear dynamics in solar wind and corona

Abstract

This paper presents a numerical simulation leading to the formation of intense magnetic filaments of kinetic Alfvén waves (KAWs) in steady state when the nonlinearity arises due to ponderomotive effects and Joule heating. The nonlinear dynamical equation for the KAW satisfies the modified nonlinear Schrödinger equation. When the plain KAW is perturbed by a transverse perturbation, filamentary structures in solar wind and coronal holes are observed. By changing the parameters of the perturbation (such as the wave number and the phase factor), filamentary structures of KAW magnetic field have been observed. The effect of the change of the dimensionless transverse wave number Γ (normalized in terms of electron’s collisionless skin depth of the KAW) plays a very important role on filamentary dynamics. Besides the study of the magnetic-field intensity, we have done various diagnostics such as phase portraits and surface plots, and also studied the power spectrum. The effect of changing the value of Γ on power spectrum is significant. The motion is found to be quasiperiodic and appears to be chaotic for different parametric regimes. The relevance of these studies in coronal heating and solar wind acceleration/turbulence has also been pointed out.