The RadiativeCooling module implements the computation of the loss of internal thermal energy
due radiation in an optically thin medium. Physically, it solves for \dot_{e}=\mathcal{L},
where we have used \mathcal{L}=-n_H^2 \Lambda (T) (where T is the gas temperature,
n_H=\rho X_H/m_p is the total hydrogen number density, and \Lambda(T)) is the
radiative cooling rate computed seperately from quantum mechanical calculations
by other plasma modeling codes, for example, Cloudy (Ferland et. al, PASP 110, 749 (1998)).
This computation becomes especially relevant for multiphase gas in astrophysical environments prevalent in the ISM, the CGM, and the ICM, for which this module has been designed.
The RadiativeCooling module implemented in Idefix follows the algorithm of the Townsend
to integrate the loss of internal thermal energy (Townsend, ApJS 181, 2 (2009)) at every timestep
in an operator split manner. The cooling rate is read from a table at runtime where the first row
is temperature (in \rm K) and second row is \Lambda (T) (in \rm erg cm^3 s^{-1}).
Note
We assume a normalization of n_H, the total hydrogen number density for the
of the cooling curve supplied by the rate table at runtime to Idefix. Different might cooling curves with
different normalisation is known to exist in literature and special attention must be given to
what is supplied to the code. Right now, this module has been tested only with the ideal gas equation of state.
We also assume the mean particle mass \mu=0.609, i.e., constant in the current implementation (appropriate
for fully ionized plasma).
It is recommended to include conversion factors between code and physical units in definitions.hpp. For example,
``
#define UNIT_LENGTH 3.086e+18
#define UNIT_DENSITY (1.0e-02*0.609*1.673e-24)
#define UNIT_VELOCITY 1.000e+05
``
The RadiativeCooling module is a submodule of the Hydro module to compute the loss of internal thermal energy (pressure)
of the gas. The parameters specific to radiative cooling are to be set in a dedicated line starting with the word
Cooling in the [Hydro] block. An example is as follows succeded by a detailed explanation.
`` Cooling Tabulated cooltable.dat Townsend TcoolFloor 1.0e+04 ``
| Entry name | Parameter type | Comment |
|---|---|---|
| cooling mode | string | Type of radiative cooling. Only Tabulated supported right now.
|
| table name | string | name/location of the cooling table w.r.t. Idefix binary to be loaded at runtime.
|
| integration method | string | Integration method to calculate the internal thermal energy loss due to radiative cooling.
Only Townsend supported right now.
|
| TcoolFloor (skip) | string | Floor temperature in K below which cooling is turned off.
|
| temperature floor | float (optional) | Default is 1.0e+04
|