The original VULCAN is a Chemical kinetics model for exoplanetary atmospheres. The theory paper of VULCAN can be found at https://arxiv.org/abs/1607.00409
VULCAN is developed with Python 3. It should also be compatibal with python 2.X.
VULCAN requires the following python packages:
- numpy
- scipy
- Sympy
- matplotlib
- PIL/Pillow (optional)
If any of the first four packages are not installed, the easiest way is to install the full SciPy Stack. e.g.
python -m pip install --upgrade pippip install --user numpy scipy matplotlib ipython jupyter pandas sympy noseThe above commands update pip and install SciPy via pip. Further information can be found at http://www.scipy.org/install.html
PIL or Pillow is a plotting library. If installed, the plots will be conveniently shown by the os-built-in image viewer. See https://github.com/python-pillow/Pillow for more information.
Go to the main folder of VULCAN, run
python vulcan.py
After the run successfully finished, we can plot the results from the output print_evolution.py The series of timesteps and mixing ratios can be access from data['variable']['t_time'] and np.array(data['variable']['y_time'])[:,0,species.index(sp)]/float(data['atm']['n_0']), respectively (data['atm']['n_0'] is the total number density).
├── VULCAN/
│ ├── atm/
│ ├── /thermo/
│ │ ├── HOC_compose.txt
│ │ ├── gibbs_text.txt
│ │ ├──/NASA9/
│ │ ├── XXX_netowrk.txt
│ ├── build_atm.py
│ ├── chem_funs
│ ├── CHO_netowrk.txt
│ ├── op.py
│ ├── prepipe.py
│ ├── plot_vulcan.py
│ ├── phy_const.py
│ ├── store.py
│ ├── vulcan.py
│ ├── vulcan_cfg.py
/atm/ : for input atmospheric files
/thermo/ : for thermodynamic data
/thermo/HOC_compose : basic physical property e.g. number of atoms and molecular weight
/NASA9/ : to store NASA-9 polynomials for the Gibbs free energy of every species
build_atm.py : modules to construct the atmospheric structure and to read in reaction rates
chem_funs.py : the functions of chemical sources, Jacobian matrix and the equilibrium constants
XXX_netowrk.txt : the kinetics network
op.py : modules for the main computation
prepipe.py : pre-pipeline routine to produce chem_funs.py
plot_vulcan.py : read-in and plotting script
phy_const.py : physical constants
store.py : modules to store all the variables
vulcan.py : the main file of VULCAN
vulcan_cfg.py : the configuration file for VULCAN
vulcan_cfg.py includes all the settings and parameters, e.g. the atmospheric parameters, the elemental abundance etc. Typically this is the only file you need to edit for each specific run. A summary of every setting is listed in vulcan_cfg_readme.txt.
The key input files of VULCAN include the chemical network and the atmospheric file.
CHO_network.txt is the deafult reaction network including carbon, hydrogen, and oxygen species. It is constructed for thermochemistry from 500 to 2500 K using a reduced network with 29 gaseous species and less than 300 reactions to benefit for efficiency. The rate coefficients A, B, C are written in A, B, C as in the Arrhenius formula k = A T^B exp(-C/T) (See the section of editing or using a different chemical network.) The input temperature-pressure profiles are placed in the /atm folder by default. As the form of the included example files for HD 189733b and HD 209458b, the first line is always commented for units, and the second line specifies the column names: Pressure Temp or Pressure Temp Kzz (if Kzz-P profile is provided). So the file consists of two columns without Kzz and three columns with Kzz. When Kzz is provided, set
Kzz_prof = 'file'in the configuration file vulcan_cfg.py.
VULCAN is developed in a flexible way that the chemical network is not hard coded. Instead, prepipe.py generates all the required funtions from CHO_netowrk.txt into chem_funs.py . prepipe.py is executed prior to the release to make chem_funs.py from the default network. Once any change is made to the file of chemical network, prepipe.py has to be executed again before running the main code to regenerate the corresponding functions, by simply run
python prepipe.py
One can examine the information, e.g. the reaction table in the comments in chem_funs.py, being updated.
You can edit the default netowrk, to remove or add reactions, to change rate constats, etc. You can also use a different chemical network, as long as it is in the same format as CHO_netowrk.txt. Noted that however, changing or using a different chemical network is not warranted, unrealistic values could lead to numerical issues. In the network file, the reactions should be writen in the form of [ A + B -> C + D ], including the square brackets. Only the forward reactions are listed, since VULCAN reverses the forward reactions to obtain the reverse reactions using the thermodynamic data. The reaction number, i.e. id, is irrelevent as it will be automatically generated (and writing into the network file) while running prepipe.py. Three-body or dissociation reactions should be separately listed after the comment line
# 3-body and Disscoiation ReactionsNext, make sure all the species are included in the NASA9 folder. If not, they need to be add manually by looking over nasa9_2002_E.txt and save them into txt files with the same name as used in the network. The format of the NASA 9 polynomials is as follows
a1 a2 a3 a4 a5
a6 a7 0. a8 a9
Noted that a7 and a8 are separated by 0. The first two rows are for low temperature (200 - 1000 K) and the last two rows are for high temperature (1000 - 6000 K).
Finally, run prepipe.py as described before.
VULCAN is distributed under the terms of the GNU General Public License (GPL) license. For more information, see GPL_license.txt in the main directory.
The project is financially support from the Center for Space and Habitability (CSH), the PlanetS NCCR framework and the Swiss- based MERAC Foundation. The Exoclime Simulation Platform (ESP) develops a set of open-source codes for research on exoplanets. The three parts of the ESP are