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Create Cooling Functions

Create Cooling Functions

The release/ absorption of energy via various physical process would modify the thermal state of the medium, which might in turn accelerates/ terminates further reactions. Keeping track of the thermal energy through the course of evolution is quintessential to the accurate modeling of the process.

Note

While it is termed cooling actions, or cooling function in dengo, it is not limited only to cooling functions. This module can account for general modifications to the thermal energy of the fluid parcel \(\frac{d\epsilon}{dt}\) whether it is injecting/ releasing energy from the fluid parcel. For example, when molecular hydrogen is formed from 3-body reactions, \(4.48 eV\) is released. We will demonstrate that how to account for the chemical heating in one of the chapters to follow.

\(k01\) is the reaction that describes the recombination of an ionized hydrogen atom with an electron. Energy is released as a result of such process.

Register new cooling functions with the cooling_action decorator

Similar to reactions, the cooling functions can be specified with a decorator dengo.reaction_classes.cooling_action. a cooling_action to dengo is primarily composed of:

  • name of the cooling function, i.e. reHII

  • Cooling Equation, -reHII * HII * de

  • Cooling Rate, that often times dependent on the temperature of the gas parcel, and sometimes on external factors as well.

In the example below, HII and de are defined and registered in dengo species registry. reHII the cooling rate associated to this particular cooling function. The cooling rate takes eq as an input. @eq.table register the cooling rates that are dependent on temperature. From then on dengo would associate the symbol reHII appeared in the cooling equation to the user-supplied cooling rate def reHII(state) internally.

from dengo.reaction_classes import cooling_action
from dengo.chemical_network import cooling_registry

# -- reHII --
@cooling_action("reHII", "-reHII * HII * de")
def cool(eq):
    @eq.table
    def reHII(state):
        # (from Hui and Gnedin 1997)
        lambdaHI = 2.0 * 157807e0 / state.T
        vals = 1.778e-29 * state.T * lambdaHI**1.965 / \
         (1.0e0 + (lambdaHI/0.541)**0.502)**2.697
        return vals

cooling_registry['reHII'], type(cooling_registry['reHII'])

(<dengo.reaction_classes.CoolingAction at 0x7f1aec35fd30>,
 dengo.reaction_classes.CoolingAction)

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Creating Reactions

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Creating a Network