.. _rotation:

Including Rotation
==================

This section discusses how to include the effects of rotation in GYRE
calculations. See the :ref:`osc-rot` section for further details of
GYRE's rotation treatment.

Setting the Rotation Rate
-------------------------

.. nml:group:: rot
   :no-target:

There are two different ways to define the rotation angular frequency
:math:`\Orot`, via options in the :nml:group:`rot` namelist group.

* If :nml:option:`Omega_rot_source` = :nml:value:`'MODEL'`, then
  differential rotation is assumed with a spatially varying
  :math:`\Orot` obtained from the stellar model. If the model doesn't
  have this capability (see the :ref:`model-caps` section), then
  :math:`\Orot` is set to zero throughout the star.

* If :nml:option:`Omega_rot_source` = :nml:value:`'UNIFORM'`, then
  uniform rotation is assumed with a spatially constant :math:`\Orot`
  set by the :nml:option:`Omega_rot` option.

Incorporating Doppler Effects
-----------------------------

The :ref:`osc-rot-doppler` effect is incorporated automatically
whenever calculations are performed with non-zero :math:`\Orot` and
mode azimuthal order :math:`m`. To disable this effect, set
:nml:option:`m <mode.m>` = :nml:value:`0` in the :nml:group:`mode`
namelist group.

Incorporating Coriolis Effects
------------------------------

Incorporating the effects of the Coriolis force can be done using a
:ref:`perturbative treatment <osc-rot-coriolis-p>` or a
:ref:`non-perturbative treatment <osc-rot-coriolis-np>`. In the former
case the effects are be applied as a post-calculation correction to
non-rotating eigenfrequencies (see the
:ofile:field:`summary.domega_rot` and :ofile:field:`detail.domega_rot`
output fields). In the latter case, the traditional approximation of
rotation (TAR) can be enabled by setting the
:nml:option:`lambda_method <osc.lambda_method>` option to
:nml:value:`'TAR-GRAVITY'` (for gravito-acoustic modes) or to
:nml:value:`'TAR-ROSSBY'` (for Rossby modes).