.. _parameter-file:

Description of the parameters in PION parameter files
=====================================================

divide up parameters by topic and describe them in tables.


Stellar Winds
-------------

Stellar winds in PION are implemented in 3 modules: a constant wind, an evolving wind, and a latitude-dependent wind.
The parameter file for a constant wind has a number of parameters that should be set, quoted below with the expected units.  They are stored in these units in the ``SWP`` struct of type ``stellarwind_params``.

+---------------------+--------------------------------------------+-------------------------------------+
| Parameter           |   Description                              |   Units/values                      |
+=====================+============================================+=====================================+
| WIND_[i]_pos[n]     | Star position :math:`n\in[0,1,2]`          | cm                                  |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_radius     | Radius of wind injection region            | cm                                  |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_type       | [Constant, evolving, latitude  dependent]  | [0,1,2]                             |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_mdot       | Mass-loss rate from star                   | :math:`\mathrm{M_{\odot}\,yr}^{-1}` |
|                     | \(\dot{M}\)                                |                                     |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_vinf       | Terminal velocity of wind                  | :math:`\mathrm{km\,s}^{-1}`         |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_vrot       | Equatorial rotation velocity               | :math:`\mathrm{km\,s}^{-1}`         |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_temp       | Effective Temperature of star,             | K                                   |
|                     | :math:`T_\mathrm{eff}`                     |                                     |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_Rstr       | Radius of star                             | cm                                  |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_Bstr       | Strength of surface magnetic field         | Gauss                               |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_TR[n]      | Value of tracer :math:`n` in wind          | Usually :math:`\in [0,1]`           |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_evofile    | Text file with data for evolving wind      | Default is NOFILE                   |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_t_offset   | offset of sim time from evolution time     | Default is 0.0                      |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_t_scalefac | scaling simulation time to evolution time  | Default is 1.0                      |
+---------------------+--------------------------------------------+-------------------------------------+
| WIND_[i]_updatefreq | How often to update the wind               | seconds                             |
+---------------------+--------------------------------------------+-------------------------------------+
|WIND_[i]_enhance_mdot| ad-hoc flag to increase :math:`\dot{M}`    | Default is 0                        |
+---------------------+--------------------------------------------+-------------------------------------+

For constant winds, these data are stored in the global struct ``SWP``, defined in
``pion/source/constants.h``, using these units.  In simulation snapshots they also have the
same units.  
The evolving wind file should have all units in CGS.