Calculating a contribution function

This example shows how to calculate the contribution function of a particular transition of a particular ion, at given temperatures and densities.

import astropy.units as u
import matplotlib.pyplot as plt
import numpy as np

from astropy.visualization import quantity_support

from fiasco import Ion

quantity_support()

<astropy.visualization.units.quantity_support.<locals>.MplQuantityConverter object at 0x7f5c997c3590>

Specify the plasma properties; note that an Ion has to be created with a range of temperatures, but the density is only used later in the contribution function calculation.

Te = np.geomspace(0.1, 100, 51) * u.MK
ne = 1e8 * u.cm**-3

Create the ion object

ion = Ion('O 5+', Te)
print(ion)

CHIANTI Database Ion
---------------------
Name: O 6
Element: oxygen (8)
Charge: +5
Number of Levels: 268
Number of Transitions: 3706

Temperature range: [0.100 MK, 100.000 MK]

HDF5 Database: /home/docs/.fiasco/chianti_dbase.h5
Using Datasets:
  ioneq: chianti
  abundance: sun_coronal_1992_feldman_ext
  ip: chianti

Calculate the contribution function, and get the index of the transition closest to the desired wavelength

contribution_func = ion.contribution_function(ne)
wlen = 1031.93 * u.Angstrom

WARNING: No proton data available for O 6. Not including proton excitation and de-excitation in level populations calculation. [fiasco.ions]

Because the contribution function is calculated for all transitions at once, we need to get the index of the transition closest to the wavelength specified earlier.

transitions = ion.transitions.wavelength[~ion.transitions.is_twophoton]
idx = np.argmin(np.abs(transitions - wlen))

Plot the result

plt.plot(Te, contribution_func[:, 0, idx],
         label=f'{ion.atomic_symbol} {ion.charge_state}+ {wlen}')
plt.title('Contribution function')
plt.xscale('log')
plt.yscale('log')
plt.legend()
plt.show()