Spectral Properties of Acoustic Gravity Wave Turbulence

TL;DR

This paper investigates the nonlinear turbulence of acoustic gravity waves in Earth's atmosphere using 2D fluid simulations, revealing a Kolmogorov-like spectrum and large-scale flow generation.

Contribution

It introduces a coupled two-component model for acoustic gravity wave turbulence and characterizes its spectral and flow properties.

Findings

Turbulent spectrum exhibits a $k^{-5/3}$ Kolmogorov-like scaling.

Large scale velocity potential flows are generated along the vertical direction.

Cross field diffusion grows linearly and saturates in the nonlinear phase.

Abstract

The nonlinear turbulent interactions between acoustic gravity waves are investigated using two dimensional nonlinear fluid simulations. The acoustic gravity waves consist of velocity and density perturbations and propagate across the density gradients in the vertical direction in the Earth's atmosphere. We find that the coupled two component model exhibits generation of large scale velocity potential flows along the vertical direction, while the density perturbations relax towards an isotropic random distribution. The characteristic turbulent spectrum associated with the system has a Kolmogorov-like feature and tends to relax towards a $k^{-5/3}$ spectrum, where $k$ is a typical wavenumber. The cross field diffusion associated with the velocity potential grows linearly and saturates in the nonlinear phase.