fundamental mode

[mjoyce]

Apologies in advance if this is somewhere on the FAQ!

I've gotten into several "enthusiastic discussions" with people (observers) about why GYRE labels the FM as n = 0 rather than n = 1. Each time, it makes me question whether I'm actually correct in my understanding of GYRE's convention.

First, can I get the ultimate, definitive answer on whether GYRE does indeed label the (pressure) FM as n = 0?

And if so, why is that the convention?

Cheers,

[rhtownsend]

Hi Meridith --

Thanks for your question. Can you give a specific example of GYRE labeling the FM as n=0? Because I don't think it does!

cheers,

Rich

[mjoyce]

Thanks Rich

Digging through my very poorly organized notes on my 2018 and 2019 papers over the past few days, I think this must have been a case of my misunderstanding what n_p and n_pg meant a while ago, and then that misconception propagating forward.
I'm not an asteroseismologist by training, so there are many gaps in my understanding of terminology and convention, etc. Slowly being rectified by eavesdropping on the Sydney group

Maybe you should host a GYREfest someday!

[rhtownsend]

Hi Meridith --

Thanks for the clarification!

For the record, n_p counts the number of wavefunction nodes in acoustic propagation zones, and n_g the corresponding number of nodes in gravity-wave propagation zones. These countings neglect any node at the center, *except* for radial modes where the center point is always counted as a node.

For radial modes, there is no gravity-wave propagation zone (you can't have radial gravity waves), and so n_g = 0 always. Due to the node that's always counted at the center, n_p is always >= 1.

The overall mode classification assigned by GYRE, is defined as n_pg = n_p - n_g (there's some special casing for dipole, l=1 modes, but that's a separate matter). For radial modes, we therefore have n_pg (the "radial order") >= 1.

Hope that clarifies!

Best wishes,

Rich