Wind.ionization
The approach used by SIROCCO to calculate the ionization of the wind during ionization cycles. A number of these modes are historical or included for diagnostic purposes.
- Type
Enumerator
- Values
- on.the.spot
Use a simple on-the-spot approximation to calculate the ionization.
- LTE_te
Calculate ionization based on the Saha equation using the electron temperature. The electron temperature is not iterated; it remains at the value set during initialization (from Wind.t.init, or from the imported model for hydro winds). (This is intended as a diagnostic mode.)
- LTE_tr
Calculate ionization based on the Saha equation using the radiation temperature. Unlike LTE_te, the radiation temperature is updated each cycle from the mean frequency of the radiation field estimated during photon transport, so the ionization evolves as the radiation field converges. The electron temperature is not iterated. (This is intended as a diagnostic mode.)
- LTE_iterate
Calculate ionization using the Saha equation at the electron temperature, with the electron temperature determined by balancing heating and cooling. Both ion populations and partition functions are calculated in LTE. Unlike other modes, here, both the heating and cooling are changed as part of the iteration proces. At each trial temperature, the Saha equation is solved to update ion densities, and the heating is scaled to reflect the new densities. Specifically, the routine scales heated recorded during photon transfer by the ratio of the original ion density for each cycle to the trial densites for photoionization and Auger heating. Similarly, for free free, Compton and line heating are scaled by the electron density. This approach is more self-conistent than modifying only the cooling. As is the case for other most modes, changes are dampted with results from the previous ionization cycle to prevent changes from being too large between ionization cycles. This mode is intended for situations where LTE ionization is physically appropriate and one wants to determine the electron temperature self-consistently.
- ML93
Use the modified on-the-spot approximation described by Mazzali & Lucy 1993. At each ionization cycle, the electron temperature is set to t_e = 0.9 * t_r. Ionization fractions are first computed using the Saha equation at t_r, then corrected using the Lucy-Mazzali estimators which account for the dilute, non-Planckian radiation field. The partition functions are evaluated using the dilution factor W. This mode does not attempt to balance heating and cooling to determine t_e self-consistently.
- fixed
Read the ion aboundances in from a file. All cells will have the same abundances. (This is intended as a diagnostic mode, mainly to investigate the details of raditive transrfer. It should be used with caution. In particular, if the elements for which abundances are provided differ from the elements to be used as described in the elements/ions portion of the atomic data, then one should not expect the calculated electron density to be that that comes simply from the fixd concetnrations file.)
- matrix_bb
Estimate photoionization rates by approximating the spectrum in each cell based on the radiation temperature and an effective weight. Invert the rate matrix equations to calculate the ionization
- matrix_pow
Estimate photionization rates by approximating the spectrum in a cell by a piecewise approximation, usually a power law. Invert the rate matrix equation to calculate the ionization. (This is the preferred ionization mode for most calculations)
- matrix_est
Estimate photoionization rates by calculating rates directly from the photons that pass through a cell. There is no attempt to model the spectrum. Invert the rate matrix equation to calculate the ionization.
- matrix_multi
Similar to matrix_pow, except in this case a more aggessive approach to reaching ion state/temperature balance is attempted. With matrix_pow and the various other matrix methods, a single attempt is made to balance heating and cooling and then a new ionization state is calculate based on the derived electron temperature. With this method, an interation is performed, with this process being carried out multiple times. Currently number of iterations is fixed and set by the parameter NEBULARMODE_MATRIX_MULTISHOT which can be found in sirrocco.h. This mode was developed to accelerate convergence in dense plasmas, but is still regarded as somewhat experimental as of 2025 Sept.
- File
- Child(ren)