Jim Fuller edited Mode Visibility.tex  about 9 years ago

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\section{Mode Visibility}  Solar-like oscillations are driven by stochastic energy input in the acoustic cavity, which is located in the convective envelope. At its time-averaged equilibrium amplitude, the energy input and damping rates of the mode are equal \cite{Dupret_2009}.   %Modes suppressed via the magnetic greenhouse effect have an extra source of damping determined by the rate at which energy leaks through the evanescent region separating the acoustic cavity from the g-mode cavity.   Waves with angular frequency $\omega \sim \omega_{\rm max} = 2 \pi \nu_{\rm max}$ are excited via convective motions, the waves propagate downward as acoustic waves until their frequency is less than the local Lamb frequency for waves of angular degree $\ell$, i.e., until $\omega = L_l = \sqrt{l(l+1)} c_s/r$, where $c_s$ is the sound speed. At this boundary, part of the wave flux is reflected, and part of it tunnels through. The wave resumes propagating inward as a gravity wavewhen  inreaches  the radiative core where $\omega < N$, with $N$ the Brunt-Vaisala frequency. In normal red giants, wave energy that tunnels into the core eventually tunnels back out to produce the observed oscillation modes. We show here that the visibility of suppressed modes can be explained if wave energy leaking into the core never returns to the stellar envelope.