Nonlinear effects associated with kinetic Alfvén wave in magnetic islands

Abstract

Observations show that kinetic Alfvén waves (KAWs) play a very important role in turbulence as well as in magnetic reconnection and have also been a topic of debate in the context of particle heating. In this paper, we aim to investigate the effect of magnetic islands on the dynamics of the nonlinear KAW. The formation of current sheet/coherent structures has been explored due to the propagation of the nonlinear KAW through the chain of pre-existing fully developed chain of magnetic islands. It is found that the field localization is more intense when the density perturbation due to nonlinearity and the field perturbation due to background islands are taken into account in comparison to the perturbation created by both the sources separately. Thus, it is expected that both nonlinearity and islands (reconnection generated) will aid the field localization and hence turbulence. Based on these coherent structures, we have evaluated the power spectrum and found the scaling after first breakpoint to be consistent with the observation by Chaston et al. [Phys. Rev. Lett. 102, 015001 (2009)] in the ion diffusion region of the magnetotail.