AMPLITUDE EQUATIONS FOR NONADIABATIC NONRADIAL PULSATORS

The amplitude equation formalism is extended to nonradial stellar puls ators. The resultant amplitude equations describe mode excitation and coupling, and they govern the nonlinear behavior of the amplitudes of the dominant modes. The amplitudes can be directly related to the inte nsities of the Fourier spectrum of the observed light-curves. Nonadiab atic effects are fully incorporated in our formalism. The formalism ap plies, in principle, to any amount of stellar rotation and magnetic fi elds. In this paper explicit expressions are given for the nonlinear c oupling coefficients up to third order for nonrotating, nonmagnetic st ars. The inclusion of slow rotation is investigated in a companion pap er.