Jim Fuller edited section_Magneto_Gravity_Waves_In__.tex  about 9 years ago

Commit id: c3673badf80d10bc14ca3971f0ea4cec97a7e2a5

deletions | additions      

       

\label{eqn:vamin}  2 \mu v_A > \frac{\omega^2}{N k_\perp} \, .  \end{equation}  This occurs approximately where the Alfven speed is larger than the radial component of the non-magnetic gravity wave velocity, i.e., where $v_A \gtrsim v_{g,r}$. Magneto-gravity waves are evanescent in regions in which where  $\omega < \omega_{\rm MG}$, where and  $\omega_{\rm MG}$ is the magneto-gravity frequency defined as \begin{equation}  \label{eqn:maggrav}  \omega_{MG} = \sqrt{2 v_A N k_\perp} \, .  \end{equation}  In a magnetized red giant core,the value of  both $N$ and $v_A$ will typically  increase from the exterior of the radiative zone inward. Incoming gravity waves become increasingly Alfvenic magneto-gravity waves as they propagate inward  toward the helium core. If the magnetic field strength becomes hydrogen burning shell. In stars with  large enough field strengths  to satisfy equation \ref{eqn:magnetogravity2}, the \ref{eqn:vamin} somewhere in their core, incoming gravity  waves are very strongly altered by will become evanescent where $\omega=\omega_{\rm MG}$. At this point,  the magnetic field. They may waves must  either reflect(i.e., they become evanescent as in equation \ref{eqn:magnetodisp3}),  or they may transform be transmitted  into purely the strongly magnetized region as  Alfven waves. Both processes are likely In both cases, the waves will be prevented from returning  to occur for an arbitrary field geometry. the surface of the star to be observed as solar-like oscillations.  \subsection{Magnetic Greenhouse Effect}