The GYRE Forums

Hi Rich and gyre users,

In one nonadiabatic calculations of g modes of a DA white dwarf, I find there exists an adiabatic mode with radial node number = -17, but the nonadiabatic modes do not have this node number. Both 16 and 18 node modes exist in both ad and non-ad modes. What might be the reason please?

Note: the compositional gradient at the H-He transition and He-metal transition makes a bump for the brunt-vaisala frequency. I was guessing that maybe this is the reason for skipping some node number. But it does not explain why the adiabatic modes do not skip this node number, since the non-adiabatic effect is small, i.e. the imaginary part of omega << the real part of omega in the nonadiabatic calculation.

Any thought, clue, or suggestion is appreciated

Many thanks!

Sincerely,
Jing

jingluan wrote:Hi Rich and gyre users,

In one nonadiabatic calculations of g modes of a DA white dwarf, I find there exists an adiabatic mode with radial node number = -17, but the nonadiabatic modes do not have this node number. Both 16 and 18 node modes exist in both ad and non-ad modes. What might be the reason please?

Note: the compositional gradient at the H-He transition and He-metal transition makes a bump for the brunt-vaisala frequency. I was guessing that maybe this is the reason for skipping some node number. But it does not explain why the adiabatic modes do not skip this node number, since the non-adiabatic effect is small, i.e. the imaginary part of omega << the real part of omega in the nonadiabatic calculation.

Any thought, clue, or suggestion is appreciated

Many thanks!

Sincerely,
Jing

Hi Jing --

For non-adiabatic calculations, GYRE bases the radial order on the non-adiabatic radial and horizontal displacement eigenfunctions. Sometimes, these eigenfunctions can differ sufficiently from their adiabatic counterpart that an additional node appears -- or one node disappears. This then causes an apparent missing mode (or an extra mode) when you calculate the mode spectrum.

Fundamentally, the issue is that mode classification by counting nodes is only guaranteed to be successful (i.e., monotonic radial orders) for the adiabatic case.

cheers,

Rich