Switching Between Whistler‐Mode Waves on Inhomogeneities of the Plasma Density and Magnetic Field

Abstract

We present results from the investigation of a transition between two whistler‐mode waves with the same frequency and the parallel wavelength but different perpendicular wavenumbers in the inhomogeneous media consisting of the plasma density and the background magnetic field. We consider transverse inhomogeneities of these quantities. We demonstrate that there are critical values of the plasma density and the magnetic field (which depend on the wave frequency and the parallel wavelength) and the switching between two whistler‐mode waves occurs in the vicinity of these values. We analyze this problem assuming that these critical values are reached inside the finite‐size transition layer between two regions where all the background quantities are homogeneous. We found analytical criteria for the mode switching and we confirmed our results with time‐dependent simulations of the electron‐MHD equations describing whistler‐mode waves in the magnetospheric plasma. We also investigate numerically the dependency of various parameters of the wave switching on the size of the transition region containing critical values of the plasma density and the magnetic field.

Whistler‐Mode Waves on Density and Magnetic Shelves

“…This wave propagates with two distinct perpendicular wavelengths, k ⊥ 1 = 1.16 rad/km (λ ⊥ 1 = 5.41 km) and k ⊥ 2 = 4.52 rad/ km (λ ⊥ 2 = 1.4 km). The whistler-mode wave interacting with the magnetic inhomogeneity at B = B 2 undergoes mode-switching where the wave vector magnitudes exchange k ⊥ 1 ⇔ k ⊥ 2 Nejad and Streltsov (2024a). This behavior occurs as the wave follows regions with lower magnetic fields, aligning with the dispersion curve (see Figure 2a').…”

“…The density and magnetic profiles are taken to have a width of 150 km across B 0 . Since the size of the transition region does not change the physics of the reflection and mode transition of the interacting whistler-mode waves Nejad and Streltsov (2024a), the transition regions' thickness for all density and magnetic shelf structures' simulations are set to 10 km on each side of the shelf.…”