Onset of Nonlinear Internal Gravity Waves in Intermediate-Mass Stars

Abstract

Internal gravity waves (IGW) propagate in the radiation zones of all stars. During propagation, their amplitudes are affected by two main features: radiative diffusion and density stratification. We have studied the implications of these two features on waves traveling within the radiative zones of non-rotating stars with stellar parameters obtained from the one dimensional stellar evolution code, MESA. As a simple measure of induced wave dynamics, we define a criterion to see if waves can become nonlinear and if so, under what conditions. This was done to understand the role IGW may play in angular momentum transport and mixing within stellar interiors. We find that the IGW generation spectrum, convective velocities and the strength of density stratification all play major roles in whether waves become nonlinear. With increasing stellar mass, there is an increasing trend in nonlinear wave energies. The trends with different metallicities and ages depend on the generation spectrum.