Wavevector spectral signature of decay instability in space plasmas

Abstract. Identification of a large-amplitude Alfvén wave decaying into pair ion-acoustic and daughter waves is one the major goals in observational studies space plasma nonlinearity. In this study, decay instability analytically evaluated 2-D wavenumber domain spanning parallel perpendicular directions to mean magnetic field. The growth-rate determination density perturbations based on Hall MHD (magnetohydrodynamic) wave–wave coupling theory for circularly polarized waves. diagrams growth rates versus propagation angle derived analytical are replaced by distributions compared with corresponding wavevector spectrum field fluctuations. actual study reveals spectral pattern consistent result previous 3-D hybrid numerical simulations. signature observed two-dimensional ceases at values beta larger than β=0.1. Growth-rate maps serve as useful tool predictions or fluctuations various scenarios processes developing different stages turbulence.