Nonlinear evolution of the r-modes in neutron stars.
TL;DR: The evolution of a neutron-star r-mode driven unstable by gravitational radiation is studied here using numerical solutions of the full nonlinear fluid equations to study the nonlinear evolution of the mode.
Abstract: The evolution of a neutron-star $r$-mode driven unstable by gravitational radiation is studied here using numerical solutions of the full nonlinear fluid equations. The dimensionless amplitude of the mode grows to order unity before strong shocks develop which quickly damp the mode. In this simulation the star loses about $40%$ of its initial angular momentum and $50%$ of its rotational kinetic energy before the mode is damped. The nonlinear evolution causes the fluid to develop strong differential rotation which is concentrated near the surface and poles of the star.
Cites background from "Nonlinear evolution of the r-modes ..."
...However, Arras et al. (2003) found that the r-mode waves saturate at amplitudes lower than obtained in previous numerical calculations (Lindblom et al. 2001) that assumed an unrealistically large driving force....