Direct Ionization ################# This is the data to compute ionization rates from collisions between ions and hot electrons. Source ====== The data comes directly from `Dere 2006, A&A, 466, 771 `_ . This paper gives direct ionization and excitation-autoionization rate coefficients for many ions as a function of temperature for Maxwellian electron distributions. Translation to SIROCCO format ====================================== The data table is downloaded in its entirety from the data table associated with the paper. All that happens is that the table is saved to a text file, and the keyword DI_DERE is just prepended to each row. Data format =========== Each line starts with the label DI_DERE and then follows - Nuclear Charge - z - used to identify the ion - Ion - state in our normal notation, so 1=neutral - Number of splines N- the number of spline points for the fit of rate coefficients vs scaled temperature - Scaled temperatures - there are N of these - Scaled Rate coefficients - N of these The scaled temperatures are given by :math:`x=1-\frac{\log{f}}{\log(t+f)}` where :math:`t=kT/I`. :math:`I` is the ionization potential, and :math:`f=2.0`. The rate coefficient R(T) is recovered from the scaled rate coefficient in the table, :math:`\rho` using :math:`\rho=t^{1/2}I^{3/2}R(T)/E_{1}(1/t)` where :math:`E_{1}` is the first exponential integral. In python we use the gsl_sf_expint_E1 routine in gsl. SIROCCO structure ========================== This data is stored in the dere_di_rate structure with members - int nion- Internal cross reference to the ion that this refers to - int nspline - the number of spline points that the fit is evaluated over - double temps[DERE_DI_PARAMS]- temperatures at which the rate is tabulated - double rates[DERE_DI_PARAMS]- rates corresponding to those temperatures - double xi - the ionization energy of this ion - double min_temp -the minimum temperature to which this rate should be applied Comments ======== This data is also in Chianti , although in a different form. So we could potentially use this data as part of a push to just use Chianti for all our data uses. An updated set of DI data is available `here `_