Parametric decay of oblique Alfv\'en waves in two-dimensional hybrid simulations

TL;DR

This study uses two-dimensional hybrid simulations to investigate the parametric decay of oblique Alfvén waves, revealing how such waves can decay into other waves with different wavenumbers, which was computationally challenging before.

Contribution

First 2D hybrid simulation analysis of oblique Alfvén wave decay, demonstrating decay into waves with varied wavenumbers under realistic plasma conditions.

Findings

Oblique Alfvén waves can decay into waves with higher and lower wavenumbers.

Hybrid simulations effectively model parametric decay in two dimensions.

Decay behavior depends on wave obliquity and polarization.

Abstract

Certain types of plasma waves are known to become parametrically unstable under specific plasma conditions, in which the pump wave will decay into several daughter waves with different wavenumbers and frequencies. In the past, the related plasma instabilities have been treated analytically for various parameter regimes and by use of various numerical methods, yet the oblique propagation with respect to the background magnetic field has rarely been dealt with in two dimensions, mainly because of the high computational demand. Here we present a hybrid-simulation study of the parametric decay of a moderately oblique Alfv\'en wave having elliptical polarization. It is found that such a compressive wave can decay into waves with higher and lower wavenumbers than the pump.