[Chemistry]

This header describes the chemical composition of the atmosphere. The type of model used is defined by the chemistry_type variable.

The available chemistry_type are:
  • ace
    • ACE equlibrium chemistry

    • Class: ACEChemistry

  • taurex
  • custom

ACE Equlibrium Chemistry

Warning

Since version 3.1 this has been removed from the base TauREx package. You can restore this chemical scheme by writing:

pip install taurex_ace

chemistry_type = ace chemistry_type = equilibrium

Equilibrium chemistry using the ACE FORTRAN program. Fortran compiler required

Keywords

Variable

Type

Description

Default Value

metallicity

float

Stellar metallicity in solar units

1.0

co_ratio

float

C/O ratio

0.54951

Fitting Parameters

Parameter

Type

Description

ace_metallicity

float

Stellar metallicity in solar units

ace_co

float

C/O ratio


Taurex Chemistry

chemistry_type = taurex chemistry_type = free

This chemistry type allows you to define individual abundance profiles for each molecule. Molecules are either active or inactive depending on whats available. If no cross-sections are available then the moelcule is not actively absorbing.

Keywords

Variable

Type

Description

Default

fill_gases

str or list

Gas or gases to fill the atmosphere with

H2,He,

ratio

float or list

Ratio between first fill gas and every other fill gas

0.749

Fitting Parameters

On its own, this chemistry model provides fitting parameters relating to the fill gases used. These are only created when more than one fill gas is defined. Here, we use [Gas-0] to designate the first gas defined in the fill gas list and [Gas-(number)] to designate the nth gas after the main gas. If we have a gas list like:

fill_gases = H2,He,CO2,

then [Gas-1]_[Gas-0] == He_H2 and [Gas-2]_[Gas-0] == CO2_H2:

Parameter

Type

Description

[Gas-(n)]_[Gas-0]

float

Ratio of nth fill gas vs first fill gas

However molecules are defined as subheaders with the subheader being the name of the molecule. Each molecule can be assigned an abundance profile through the gas_type variable. For example, to describe a chemical profile with water in constant abundance in the atmosphere is simply done like so:

[Chemistry]
chemistry_type = taurex
fill_gases = H2,He,
ratio = 0.1524

    [[H2O]]
    gas_type = constant
    mix_ratio = 1e-4
For each molecule, the available gas_type are:
  • constant
  • twopoint
    • Two Point abundance profile

    • Class: TwoPointGas

  • twolayer

Gas Profiles

For these profiles, the fitting parameters generated have the name associated with the name of the molecule. For example: H2O_P, CH4_S etc. Because of this, we will use the moniker: [Mol]. Replacing this with the appropriate molecule will give you the correct fitting parameter name. e.g. [Mol]_surface should be H2O_surface for water etc.

Constant Profile

gas_type = constant

An abundance profile that is constant with height of the atmosphere

../../_images/constantgas.png

Keywords

Variable

Type

Description

Default

mix_ratio

float

Mixing ratio of molecule

1e-4

Fitting Parameters

Parameter

Type

Description

[Mol]

float

Mixing ratio of molecule


Two Layer Profile

gas_type = twolayer

An abundance profile where abundance is defined on the planet surface and top of the atmosphere with a pressure point determining the boundary between the layers. Smoothing is applied.

../../_images/twolayerabundance.png

Keywords

Variable

Type

Description

Default

mix_ratio_surface

float

Mixing ratio at BOA

1e-4

mix_ratio_top

float

Mixing ratio at TOA

1e-8

mix_ratio_P

float

Pressure boundary (Pa)

1e3

mix_ratio_smoothing

int

Smoothing window

10

Fitting Parameters

Parameter

Type

Description

[Mol]_surface

float

Mixing ratio at BOA

[Mol]_top

float

Mixing ratio at TOA

[Mol]_P

float

Pressure boundary (Pa)


Chemsitry File

chemistry_type = file

Reads a multi-column text file. Order must be from BOA to TOA. Each column must represent a unique molecule.

Keywords

Variable

Type

Description

Default

filename

str

Path to chemistry file

None

gases

list

List of all molecules in column order

None