Line Transfer

Astrobear currently supports 1D Line Transfer of ionizing radiation in the +x direction. To enable this you will need to use the MultiSpecies EOS, turn on Hydrogen Tracking, set iLineTransfer=1 and LineTransferFlux to whatever value you would like (in units of cm^-2 s^-1)

• iEOS=1
• lTrackHydrogen=T
• iLineTransfer = 1
• LineTransferFlux=2e13

This will turn on photo-ionization of hydrogen, ionization heating, recombination, recombination cooling, and Lyman alpha cooling.

Photo Ionization

Photoionization of neutral hydrogen is given by

I_{ph}=F e^{-\tau} \sigma n_H

with

\sigma= 6.3\times 10^{-18} cm^2

\tau=\int \sigma n_H dx

and

F is the value set in physics.data for LineTransferFlux and

Photo Ionization Heating

\frac{de}{dt}=e_\gamma I_{ph}

with e_\gamma=2.4 eV

Recombination

The recombination rate is

R=\alpha n_e n_{H+}

with \alpha = 2.59\times 10^{-13}(T/10^4 K)^{-0.7} cm^3 s^{-1}

Recombination Cooling

Recombination cooling is given by \frac{de}{dt}= -\Lambda_{rec} n_e n_{H+}

with

\Lambda_{rec}=6.11 \times 10^{-10} cm^3 s^{-1} k_BT \left(T/K\right)^{-.89}

Lyman alpha cooling

Lyman alpha cooling is given by

\frac{de}{dt}=-\Lambda_{\alpha} n_e n_H

with

\Lambda_{\alpha} = 7.5 \times 10^{-19} \mbox{erg cm}^{3} \mbox{s}^{-1} e^{-118348 K/T}

Time Stepping

Currently this only works in fixed grid so MaxLevel needs to be set to 0 in global.data

The linetransfer step happens after the hydro update and it sub-cycles as many times as necessary to prevent the number densities of neutral or ionized hydrogen as well as the internal energy from changing by more than 10%. It currently does not constrain the hydro time step.

Also note that normally lTrackHydrogen = True enables a separate module that does collisional ionization and recombination (and there associated cooling), but those are turned off if iLineTransfer=True