On nonlinear decay of kinetic Alfvén waves and application to some processes in space plasmas

Abstract

[1] This paper considers the nonlinear decay of the kinetic Alfvén waves (KAW) in the space plasmas. By using a two-fluid model, we obtain a nonlinear equation to investigate the resonant interaction among three kinetic Alfvén waves. It is shown that the parametric instability of the kinetic Alfvén wave becomes important when its perpendicular wavelength is the order of the ion acoustic gyroradius or the electron inertial length. We give a detailed discussion for the KAW decay in the plasma inertial range and show that (1) the reverse decay of the kinetic Alfvén wave is stronger than its parallel decay for the arbitrary wavelength range; (2) the reverse decay is lager than the parallel decay for small angles of two perpendicular wave vectors of the decay waves, and these two decays are zero for large angles; (3) both growth rates depend on the choice of the wave number range of the decay waves; and (4) there exists two forbidden regions for the KAW decay. In this paper, we also discuss the nonlinear decay of the kinetic Alfvén waves in the auroral zone and show that the parametric instability can occur there and may play an important role in forming two reverse electron streaming fluxes in the electron acceleration region.

A nonlocal wave-wave interaction among Alfvén waves in an intermediate-β plasma

“…[32][33][34][35][36][37] A large amplitude dispersive Alfvén wave can bring about the local nonlinear decay among themselves. [34][35][36][37] Local interaction between two counterpropagating Alfvén wave packets can lead the wave energy to cascade from the energy injection region to the energy dissipation region in the MHD turbulence. 32,33,[38][39][40] Through the local cascade, the KAW can be generated at scales of the order of the ion inertial length or the ion gyroradius in the solar wind turbulence; [41][42][43][44] however, it cannot reach electron scales ͑the electron inertial length or the electron gyroradius͒ due to the large electron Landau damping in these small scales.…”

Nonlinear interaction and parametric instability of kinetic Alfvén waves in multicomponent plasmas

“…16,17,21 For three-component plasmas, the perpendicular convective motion of the heavy ions is as important as the other nonlinearities. The self-interaction among the KAWs can result in parametric instabilities.…”

“…[15][16][17][18] Voitenko 19,20 pointed out two cases of KAW decay in the kinetic regime: the parallel decay in which the two decay waves are in the same direction and the reverse decay in which the two decay waves are in opposite directions. More recently, Zhao et al 21 reconsidered these two decays in the inertial regime and showed that the reverse decay is stronger than the parallel decay. Furthermore, it is shown that the reverse decay can occur in the Earth's electron-acceleration zone, which can be associated with the counter propagating electron fluxes frequently observed there.…”

“…Furthermore, it is shown that the reverse decay can occur in the Earth's electron-acceleration zone, which can be associated with the counter propagating electron fluxes frequently observed there. 21 However, the above studies are limited to two-component plasmas. Many in situ observations indicate that there are heavy ions (He, C, O, Ne, Mg, etc.)…”

Potential role of kinetic Alfvén waves and whistler waves in solar wind plasmas

“…Because the electron thermal speed exceeds the Alfvén speed, the electrons respond adiabatically to the wave fields. The nonlinear properties of KAW convey its theoretical and analytical usefulness (Zhao et al 2010(Zhao et al , 2011(Zhao et al , 2012. Highly oblique KAW are considered good candidates for the observed solar wind turbulence spectrum at scales below ion gyro-radius (Howes 2015).…”