Non-radial mode frequencies in Red Giants

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Non-radial mode frequencies in Red Giants

Post by sanjay » Mon Apr 23, 2018 9:37 am

Hi All,

I have been using GYRE 5.1 to output l=0, and l=2 and l=3 p-mode frequencies from a Red-Giant MESA model. According to scaling relations, the nu_max of the model is around 30 microhertz. However, the lowest frequency of the l=2 and l=3 modes is above 150 microhertz:
strange_brew.png (36.4 KiB) Viewed 736 times
Could someone please explain to me why I'm getting such a result? One would naively expect that the higher-degree modes also span the frequency regime around nu_max.


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Re: Non-radial mode frequencies in Red Giants

Post by rhtownsend » Mon Apr 23, 2018 10:13 am

Hi Sanjay --

Because you are modeling a red giant you can expect to find mixed modes, that are g modes in the core and p modes in the envelope. These modes will generally have radial orders n_pg which are less than zero.

Looking at your input file, I note that you set n_pg_min = 1 in the &mode inlist groups. This means that all the modes with n_pg <= 0 (i.e., the mixed modes) get thrown away when GYRE finds them.

The solution is simple: remove the n_pg_min settings from your input file.



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