A Nonlinear Coupling Network to Simulate the Development of the r-mode   Instablility in Neutron Stars I. Construction
  R-modes of a rotating neutron star are unstable because of the emission of gravitational radiation. We explore the saturation amplitudes of these modes determined by nonlinear mode-mode coupling. Modelling the star as incompressible allows the analytic computation of the coupling coefficients. All couplings up to n=30 are obtained, and analytic values for the shear damping and mode normalization are presented. In a subsequent paper we perform numerical simulations of a large set of coupled modes. 
Jeandrew Brink, Saul A. Teukolsky, Ira Wasserman