Spectral diagnostics in the EUV - slide " 6.4 Isothermal approximation"

In the isothermal approximation, all plasma is assumed to be at a single temperature (T_o) and the intensity becomes:

I(l_ij) = C(T_o, l_ij, N_e) Ab(X) EM_h
(18)

where we have defined the column emission measure

EM_h = ó
õ N_e N_H dh [cm^-5]
(19)

Within CHIANTI, one way to obtain a spectrum in the isothermal approximation is:

 IDL > isothermal, 150., 200., 1., [1.e6], wvl, spectrum,$
       list_wvl, list_ident, edensity=1.e9,$
      ioneq_name=!xuvtop+'/ioneq/mazzotta_etal.ioneq',$
       abund_name=!xuvtop+'/abundance/cosmic.abund'

 IDL>  synthetic_plot, wvl, spectrum, list_wvl, list_ident, 1.

calculates an isothermal synthetic spectrum with a resolution of 1 Å between 100 and 200 Å for a specified set of abundances and differential emission measure at a constant density N_e = 10⁹ cm^-3. The output arrays wvl, spectrum contain the wavelengths and the intensities (in erg cm^-2 s^-1 sr^-1 Å^-1 by default).