Simulation of mode conversion at the magnetopause

Abstract

Two-dimensional (2-D) and three-dimensional (3-D) hybrid simulations are carried out for mode conversion from fast mode compressional wave to kinetic Alfvén waves (KAWs) at the inhomogeneous magnetopause boundary. For cases in which the incident fast wave propagates in the xz plane, with the magnetopause normal along x and the background magnetic field pointing along z, the 2-D (xz) simulation shows that KAWs with large wave number k x ρ i ∼ 1 are generated near the Alfvén resonance surface, where ρ i is the ion Larmor radius. Several nonlinear wave properties are manifest in the mode conversion process. Harmonics of the driver frequency are generated. As a result of nonlinear wave interaction, the mode conversion region and its spectral width are broadened. In the 3-D simulation, after this first stage of the mode conversion to KAWs with large k x , a subsequent generation of KAW modes of finite k y is observed in the later stage, through a nonlinear parametric decay process. Since the nonlinear cascade to k y can lead to massive transport at the magnetopause, the simulation results provide an effective transport mechanism at the plasma boundaries in space as well as laboratory plasmas.

On the Role of Kinetic Alfven Waves in the Magnetosheath Ion Thermalization Around the Night‐Side Magnetopause

“…Chen et al., 2015; Izutsu et al., 2012; Yao et al., 2011). Indeed, the magnetosheath is filled by a wide range of ion‐kinetic scale waves (Anderson & Fuselier, 1993; Rakhmanova et al., 2021; Sahraoui et al., 2003; Song et al., 1994; Zimbardo et al., 2010) generated either by local instabilities of anisotropic ion populations (Anderson et al., 1994; Gary & Lee, 1994; Schwartz et al., 1996) or by mode conversion from large‐scale magnetohydrodynamic (MHD) waves to ion‐kinetic scale waves (C. C. Chaston et al., 2007; Cheng et al., 2020; Johnson et al., 2001; Kim et al., 2022; Lin et al., 2012; Shi et al., 2013).…”