Contents

1  Introduction

1.1  What is CHIANTI

• the main CHIANTI homepage: http://www.chiantidatabase.org/
• SolarSoft, a programming and data analysis environment for the solar physics community. http://www.lmsal.com/solarsoft/

1.2  How to acknowledge CHIANTI

• 1 - Dere et al., 1997, AASS, 125, 149 http://adsabs.harvard.edu/abs/1997A\%26AS..125..149D
• 2 - Landi et al. 1999, AASS, 135, 339 http://adsabs.harvard.edu/abs/1999A\%26AS..135..339L
• 3 - Dere et al., 2001, ApJSS, 134, 331 http://adsabs.harvard.edu/abs/2001ApJS..134..331D
• 4 - Young et al., 2002, ApJS, 144, 135 http://adsabs.harvard.edu/abs/2003ApJS..144..135Y
• 5 - Landi et al., 2005, ApJS, 162, 261 http://adsabs.harvard.edu/abs/2006ApJS..162..261L
• 6 - Dere et al., 2009, A&A, 498, 915 http://adsabs.harvard.edu/abs/2009A\%26A...498..915D
• 7 - Landi et al., 2012, ApJSS, 744, 99 http://adsabs.harvard.edu/abs/2012ApJ...744...99L
• 7.1 - Landi et al., 2013, 763, 86 http://adsabs.harvard.edu/abs/2013ApJ...763...86L
• 8.0 - Del Zanna et al., 2015, A&A 582, A56 https://ui.adsabs.harvard.edu/#abs/2015A&A...582A..56D
• 9.0 - Dere et al., 2019, ApJ, in press http://adsabs.harvard.edu/abs/2019arXiv190205019D

1.3  Important caveats and limitations

• Level excitations occur via collisional excitation by electrons and protons, and photoexcitation from black-body or user-defined radiation fields.
• Electrons and protons have Maxwellian distribution functions. Indeed CHIANTI data include Maxwellian-averaged electron and proton collision strengths. However, it is possible to study the effects of particle distributions that are linear combinations of Maxwellians of different temperatures.
• Electrons and protons have the same temperature.
• The plasma ionization is dominated by collisions (i.e. no photo-ionization is included).
• Atomic processes affecting the ionisation state of an element can be separated from those affecting the level balance within an ion.
  A correction to the level populations due to ionization and recombination is included, but it is only valid up to densities above which metastable level populations begin to be non-negligible.
• The plasma is in a steady state.
• All lines are optically thin.
• Line emissivities are reliable only in some (extended) temperature and density ranges. The ranges of temperatures at which the original rates were calculated are normally listed in the files.
• The current ion fractions that are provided within CHIANTI have been calculated assuming equilibrium and at zero density.
• DEM files are provided only as samples of DEM curves for different physical conditions in the solar atmosphere: the intensities they generate may differ from observed values.

1.4  A short history of the package

1. The first version of the CHIANTI database was released in 1996 and is described in Dere et al. (1997).
   Young et al. (1998) used the CHIANTI database for a detailed comparison with observed EUV solar spectra to assess the diagnostic accuracy of the two data sets.
2. Version 2.0 (Landi et al. 1999) was released in April 1999. This Version adds atomic data for many of the so called minor ions (Na, P, Cl, K, Ti, Cr, Mn, Co, and Zn), not included in the first version. Because the astrophysical abundances of these elements are relatively low, only the strongest lines of these elements are observed. The addition of the minor ions is an important step in our goal to understand astrophsical spectra in detail. In addition, Version 2.0 extends the beryllium-like sequence, updates some of the data in Version 1, and provides an IDL procedure to calculate the continuum.
3. Version 3.0 of the CHIANTI database was released in September 2000 (Dere et al., 2001). In this version the database has been extended to wavelengths shorter than 50Å by including atomic data for the hydrogen and helium isoelectronic sequences, inner-shell transitions and satellite lines and several other ions. In addition, some of the ions already present in the database have been updated and extended with new atomic data from published calculations. The inclusion of the satellites has required a significant modification to the manner in which the spectra have been calculated with CHIANTI. Consequently, a new version of the IDL software has been produced.
   In November 2000 we have released a whole new CHIANTI package under SolarSoft.
4. Version 4 of the CHIANTI database, released in Sept. 2002 (Young et al., 2002). The major changes are the inclusion of proton excitation data, principally for ground configuration levels which are close in energy, and of photoexcitation.
   The fitting procedure for excitation data, both electrons and protons, has been extended to allow 9 point spline fits in addition to the previous 5 point spline fits. This allows higher quality fits to data from close-coupling calculations where resonances can lead to significant structure in the thermally-averaged collision strengths.
   With the addition of H I, He I and N I, the first neutral species have been added to CHIANTI.
   Many existing ion data-sets have been updated, in particular most ions of the nitrogen and beryllium isoelectronic sequences. Also, new ions have been added, including Ar IV, Fe VI and Ni XXI.
   The continuum routines have been re-written, including a new relativistic free-free continuum, a new free-bound, and a new two-photon continuum. New software has been written.
5. Version 5 of the CHIANTI database, released in August 2005, included ionization and recombination as mechanisms for populating excited levels, photoexcitation from any user-defined radiation field, software for taking into account non-Maxwellian velocity distributions, and new data for a large number of ions (both for new entries or for ions already in the database). Changes in the data consist of the inclusion of high-energy configurations of Fe XVII to XXIII to predict a large number of lines in the X-rays, n=3 configurations in the N-like and O-like sequences to predict a large number of lines at UV wavelengths, and new data for very important ions in the EUV wavelength range such as Fe IX, Fe XII and Fe XV. The software has been speeded considerably and a few more user-friendly features have been added.
6. CHIANTI version 6, released in July 2009, includes a complete database of ionization and recombination coefficients for the first 30 elements of the periodic table, as well as a new ionization equilibrium. We also provide IDL programs to read the rates.
   Major features (Dere et al. 2009, A&A, 498, 915) in CHIANTI 6 are:
   • inclusion of ionization and recombination rates
   • new ionization equilibrium calculation
   • improved calculation of He-like line intensities (X-rays )
   • new data for Be-like and F-like sequences ( EUV )
   • new data for Fe XVII to Fe XXIII (X-rays )
   • new data for n=3 to n=3 N-like and O-like transitions (UV )
   • some additional IDL programs:
7. Version 7 of the CHIANTI database, released in Sept 2011, includes an update for a range of ions, mostly important for the EUV and the UV.
8. CHIANTI v. 8.0, released in September 2015, includes several new entries and revises the atomic data for many ions. In particular, for ions of the He-like, Li-like, B-like, Ne-like and Na-like isoelectronic sequences, plus several important coronal iron and nickel ions. In addition, the method for computing the differential emission measure has been changed.
   Until v.8, the format of the CHIANTI files has remained the same (aside from an update in the collisional files, to allow nine-point splines). The changes that are introduced in version 8 are minor, in the sense that they only affect the format of the energy and the electron excitation files. The format of these files is different, but still fixed, i.e. the same for all the ions.
   The energy files have the same information, although the format is changed and some redundant information has been removed.
   For new ions, we have chosen not to fit the electron excitation data, but rather to provide the original rates, still in the Burgess and Tully (1992) scaled domain. For each transition, a scaled temperature is given.
   We have modified the IDL software that reads the new files. There is no backward compatibility with previous versions of CHIANTI.
   Finally, we have modified the DEM inversion program.
9. CHIANTI v. 9.0, released in March 2019, includes several new atomic data for the satellite lines at X-ray wavelengths, and a different way in which the satellite line intensities are calculated. In particular, we improve the modelling by explicitly including autoionization and dielectronic recombination processes in the calculation of level populations for several ions. Atomic data for a several ions have also been added/improved. The CHIANTI DEM program has been modified and a program to calculate SDO/AIA responses added.

1.5  How to keep updated on CHIANTI developments

• Read the CHIANTI NEWS page on the WWW.
• Read the HISTORY (software) and README (database) files in the distribution. Any news and changes are logged in these files. The first one has the details of all the software changes, while the second one describes the changes to the database. These files can be found directly in the distribution or via links on the WWW pages.
• We have a google group for comments and questions:
  https://groups.google.com/forum/#!forum/chianti 

2  What is new in version 9

3  The database structure

3.1  Directory structure and atomic data file contents

dbase/

In the top directory are the following files:

        README_CHIANTI   with the description of the current version.
        VERSION	         with the version number.

Then, there is a series of subdirectories, one for each element present in the database. 
Each element has  a subdirectory  for each ion. 
The filename prefix for each ion follows spectroscopic notation.
For example, for He, we have He I and He II subdirectories:

        he/
           he_1/
           he_2/

Then, we have a series of ancillary data that are contained in 
various subdirectories:

        masterlist/
                         has the list of the ions currently present
                         in the database
        abundance/       with elemental abundance files.
        continuum/       contains files for the continuum calculations.
        dem/             has DEM files.
        ioneq/           contains ionization fraction files.
        ip/              has ionization potentials.
        ancillary_data/instrument_responses/      with effective areas.

3.1.1  Energies

1. Index of the fine structure energy levels. This index applies to all files for this ion. Levels can be arranged in any order, although they often follow the observed or theoretical energy ordering.
2. Designation of the configuration of the level. The usual configuration format is, e.g., “3s2.3p2(2P).3d”. That is, orbitals are separated by a “.” and parent terms are placed in brackets. However, separating orbitals by white space is also present, e.g., “3s2 3p2(2P) 3d”.
3. a label string, which can be used to attach a label to a level. An example is for Fe II for which the strings are used for multiplets in the same configuration which have the same LSJ labels.
4. Integer value of 2S+1, S=spin in standard usage
5. Symbol for angular momentum L, i.e. S for L=0, P for L=1, D for L=2, etc.
6. Total angular momentum J
7. observed energy in cm⁻¹ (if there is no observed value, it is set to -1).
8. theoretical energy in cm⁻¹ (usually this is the energy from the scattering calculation, but not necessarily). If an observed energy does not exist, then the CHIANTI software uses the theoretical energy for that level. The CHIANTI theoretical energies are not necessarily the same as those of the scattering calculations. In some cases, theoretical `best guess' energies are provided. These are normally obtained by linear interpolation of the ab-initio level energies with the few experimental energies. The wavelength file has the corresponding wavelengths. Typical uncertainties of the ab-initio wavelengths are a up to several Å, while those obtained from the `best guess' energies are estimated to be around 1 Å.
9. There might be further columns but these are not read by the software.

IDL> read_elvlc, filename, l1,term, $
conf,ss,ll,jj,ecm,eryd,ecmth,erydth,ref

IDL> read_elvlc, filename, elvlcstr=elvlstr

3.1.2  Wavelengths, A-values and oscillator strengths

1. index of the lower energy level, format=i5 (consistent with the ordering in the .elvlc file)
2. index of the upper energy level, format=i5
3. wavelength in Angstroms, format=f15. If the wavelength does not connect 2 observed energy levels, the wavelength is given as a negative number. Generally wavelengths are given to three decimal places, with exceptions for very short and very long wavelength transitions. Two-photon transitions are given a zero wavelength. Also, the corrections to the inner-shell levels above the ionization limit due to autoionization are included as radiationless transitions to the ground state.
4. gf value (weighted oscillator strength), format=e15
5. A-value, format=e15. Generally this will be the radiative decay rate (or A-value) in units of s-1. It can also be the autoionization rate or the two-photon decay rate, both in units of s-1.
6. In some cases additional columns have extra information on the transition. These are not read by the software.
7. comments at the end are free format.

3.1.3  Electron collisional rates

IDL> read_scups, splfile, splstr

3.1.4  Proton rates

3.1.5  Autoionization files

1. level index of the recombining ion, format=i7. This contains the level index of the singly-ionized level in the the recombining ion corresponding to the CHIANTI .elvlc file. For simple ions such as the He-like, it is 1, the index of the ground state.
2. The level index of the energetically-higher autoionising level, format=i7. The level indices are defined in the CHIANTI .elvlc file of the recombined ion, which is in the same directory as the .auto file.
3. The autoionization rate in s⁻¹, format=i7.
4. This is free format. After the data columns, there can be a free-format string giving the transition information for the transition. This is used to aid reading the file by eye, and the transition information is not read by the software.

3.1.6  Other files

3.1.7  Corrections due to ionization/recombination

IDL> read_ionrec,ionname,rec_rate,ci_rate,temp_ionrec,luprec,lupci,status,rec_ref,ci_ref

3.1.8  New (v.9) level-resolved radiative recombination rates

IDL> zion2filename,8,6,fname
IDL> rrdata = read_rrlvl( fname, status )

3.1.9  Final comments

3.2  Additional ancillary data

4  The Software structure

• Low-level routines, that for example read the files in the database, or perform the level population calculations. These are not described here and should not be used directly by the users.
• High-level routines, that perform more complex operations and can be called from the command line. These routines usually output arrays or structures, and optionally produce plots, postscript output or ascii files. Most of them have a long list of options, commanded via KEYWORDS. Please read the headers.
• Higher-level widget-type routines. These routines are more user-friendly, and are complementary of the above class. These routines call low-level or high-level routines to perform the calculations.

4.1  Short description of the CHIANTI software

• ch_synthetic.pro, calculates (without any abundance factor) line intensities or G(T), and outputs a line intensities CHIANTI structure (see Sect.10 for details). This IDL structure can be saved and later restored in various ways, for example using ch_write_fits  and ch_read_fits.
• ch_line_list.pro takes the line intensities CHIANTI structure and creates ascii or latex files with lists of line identifications and intensities.
• make_chianti_spec.pro  This program creates the CHIANTI SPECTRUM structure (read Sect. 11 for details), that contains the synthetic spectrum, created by multiplying by the abundance factor the line intensities and adding the continuum (optional).
• Finally, a multi-purpose widget ch_ss.pro has been written. It includes all the above features.

4.2  How to find help

 IDL > temperature_ratios
 IDL > temperature_ratios,ion,wmin,wmax,Log10(tempmin),Log10(tempmax),$
 IDL > temperature,ratio,description,$
 IDL >  [pressure= ,density= , psfile= , outfile= ]
 IDL > 
 IDL > i.e.:
 IDL > temperature_ratios,'c_5',40.,50.,5.,7.,temp,rat,desc

 IDL > xdoc,'ch_synthetic'
 IDL > doc_library,'ch_synthetic'

 IDL > chkarg,'temperature_ratios
 .....
---> Call: pro temperature_ratios,ions,wmin,wmax,tempmin,tempmax,$
temperature,ratio,description,$
density=density,psfile=psfile, $
outfile=outfile,noprot=noprot, $
radtemp=radtemp,rphot=rphot,photons=photons, $
ioneq_file=ioneq_file, abund_file=abund_file, $
VERBOSE=VERBOSE

5  The CHIANTI distribution and installation

1. as an independent package within SolarSoft, a programming and data analysis environment for the solar physics community. See
   http://www.lmsal.com/solarsoft/
   for details on how to download and install the package. The database and the software are organised in a self-contained package

   $SSW/packages/chianti/ 
   
   

   with the following tree structure:

   dbase/    (database)
   doc/      (documentation, in particular the USER GUIDE)
   idl/      (IDL software)
   setup/    (supplementary setup files)
   
   

   The Solarsoft website explains how to set up a "mirror" so that the contents of the package are automatically kept up-to-date, and this is highly recommended. Note, however, that updates to the CHIANTI software are fairly infrequent between major releases, and usually only for bug-fixes.
   
   All modifications to the software are logged in the $SSW/packages/chianti/idl/HISTORY file.
   Modifications to the database are much less frequent. They are described in the $SSW/packages/chianti/dbase/README_CHIANTI file.
   We send an e-mail to the CHIANTI user group every time we make a minor release of the database available.
   Note that the contents of the SolarSoft package change on a frequent timescale normally to fix bugs caused by the use of new IDL releases.
   We recommend that you use CHIANTI within the SolarSoft framework and that you setup in your site a mirror in order to have automatic upgrades. It is easy to follow the instructions to download and setup the package.
2. On the WWW, as tar files, via the CHIANTI download page:
   http://www.chiantidatabase.org/chianti\_download.html
   Currently, the data and the software are distributed in two separate tar files. The tar files have a similar tree structure as the SolarSoft distribution.
   The IDL procedures file includes idl/gen/, a copy of the $SSW/gen/ routines. This is because some routines of the $SSW/gen/ directory are needed to run some of the CHIANTI programs.
   CHIANTI is a package, in the sense that database and progams are to be used together.
   The current version of the database must be used with the current version of the programs. Backward compatibility does not always apply.

5.1  Installing CHIANTI

• Access to the CHIANTI IDL routines. The IDL !PATH should contain the paths to the directories where the CHIANTI IDL procedures are.
• Access to the CHIANTI atomic database and ancillary data. This is done by defining the system variable !xuvtop, that should point to the CHIANTI atomic database top directory.
• The following IDL system variables need to be defined:
  • !xuvtop the top directory for the atomic database
  • !ioneq_file the default ionization equilibrium file
  • !abund_file the default elemental abundance file
  • !BCOLOR , !ASPECT

5.1.1  Installing CHIANTI within SolarSoft

 unix> setssw chianti 
 unix> sswidl 
or
 unix> sswidl 
 IDL > ssw_packages,/chianti  

5.1.2  Installing CHIANTI independently as a stand-alone

unix> gunzip [file_name].tar.gz
unix> tar xvf [file_name].tar

unix > idl
 

1. add to the IDL PATH the path of where the CHIANTI IDL routines are:

   Unix: IDL> !PATH = '+/data1/chianti/idl:'+!PATH
   Windows: IDL> !PATH = '+C:\data1\chianti\idl;'+!PATH
   VMS: IDL> !PATH = '+/data1/chianti/idl,'+!PATH
   
   

2. IDL> !PATH = EXPAND_PATH(!PATH)
    
   

   The '+' and the EXPAND_PATH are needed since the IDL routines are organised into subdirectories. The second option involves writing (UNIX) the following statement in your  /.cshrc (or  /.login) file:

   setenv IDL_PATH /usr/local/rsi/idl_4/lib:+/data1/chianti/idl
   
   

   (assuming you have the main IDL directory in /usr/local/rsi/idl_4).

3. Unix:  IDL> use_chianti, '/data1/chianti/dbase'
   Windows: IDL> use_chianti, 'C:\data1\chianti\dbase'
   
   

 !PATH = '+/data1/chianti/idl:'+!PATH
 !PATH = EXPAND_PATH(!PATH)
 use_chianti, '/data1/chianti/dbase'
 END
 

 IDL> .r start_chianti
 

 !PATH = '+/data1/chianti/idl:'+!PATH
 !PATH = EXPAND_PATH(!PATH)
defsysv,'!xuvtop', '/data1/chianti/dbase'
defsysv,'!ioneq_file','/data1/chianti/dbase/ioneq/mazzotta_etal.ioneq'
defsysv,'!abund_file','/data1/chianti/dbase/abundance/cosmic.abund'
defsysv,'!BCOLOR',0
defsysv,'!ASPECT',1.0

6  Theory and definitions - implementation within the CHIANTI IDL software

6.1  Optically thin emission lines

• N(X^+m)/N(X) is the ionization ratio of the ion X^+m relative to the total number density of element X (contained in the files in the ioneq/ directory);
• Ab(X)=N(X)/N(H) is the elemental abundance relative to Hydrogen (contained in the files in the abundance/ directory);
• N(H)/N_e is the Hydrogen density relative to the free electron density. Often assumed to be equal to 0.83, as hydrogen and helium are usually completely ionised for hot optically thin plasmas.
  See the routine PROTON_DENS described in Sect. 6.3.1 for details on how to calculate N(H)/N_e.
• The fraction n_i = [(N_j(X^+m))/(N(X^+m))] of ions X^+m lying in the state j is determined within CHIANTI by solving the statistical equilibrium equations for a number of low-lying levels of the ion including all the important collisional and radiative excitation and de-excitation mechanisms.

1. the plasma is in a steady state;
2. atomic processes affecting the ionisation state of an element can be separated from those affecting the level balance within an ion;
3. all lines are optically thin.

6.2  Electron excitation rates

IDL> read_scups, splfile, splstr

      descale_all, temp, splstr, index, ups

IDL> cc=rate_coeff('fe_13',1e6)

IDL> cc=rate_coeff('fe_13',1e6,trans=[1,20])
 Wavelength:             202.04
 Exc. rate coeff:     6.986e-09
 De-exc. rate coeff:  4.746e-09

6.3  Proton excitation rates

  2  3  2 0.000e+00 1.027e-02 8.000e+02-2.150e-13 1.052e-13 4.397e-12 \
2.232e-11 5.389e-11 8.708e-11 1.014e-10 7.658e-11-2.805e-12

      IDL> read_splups, filename, splstr, splref , /prot

      .lvl1   lower level index
      .lvl2   upper level index
      .t_type transition type
      .gf     gf value
      .de     Delta-E for transition (rydbergs)
      .c_ups  the scaling parameter
      .nspl   number of spline points
      .spl    Vector of length 9, containing spline points

      descale_all, temp, splstr, index, ups

6.3.1  The proton-to-electron ratio

IDL> print, proton_dens(6.0)
      0.84860524

IDL> print, proton_dens(6.0,/hydrogen)
      0.84860545

6.4  How to obtain all the main rates for an ion at once

IDL> input=ch_setup_ion('o_6',rphot=rphot,radtemp=radtemp,noprot=noprot, $
                   ioneq_file=ioneq_file,abund_file=abund_file, $
                   noionrec=noionrec)

6.5  The level population solver

IDL> input=ch_setup_ion('o_6')
IDL> pop_solver, input, 5e5, 1e9, pop

IDL> t=[1e5,2e5,3e5]
IDL> rates=ch_load_ion_rates('o_4',t)

   N_LEVELS        LONG               204
   AA              DOUBLE    Array[204, 204]
   AAX             DOUBLE    Array[204, 204]
   PPR             DOUBLE    Array[3, 204, 204]
   QQ              DOUBLE    Array[3, 204, 204]
   TEMP            FLOAT     Array[3]
   ION_DATA        STRUCT    -> <Anonymous> Array[1]
   MULT            FLOAT     Array[204]
   SUM_MWL_COEFFS  DOUBLE    Array[3]
   SUMTST          INT              0

IDL> rates1=ch_load_ion_rates('o_6',t)
IDL> rates2=ch_load_ion_rates('o_7',t)
IDL> rates=ch_load_2ion_rates(rates1,rates2)

   N_LEVELS        LONG               972
   AA              DOUBLE    Array[972, 972]
   QQ              DOUBLE    Array[3, 972, 972]
   AAX             DOUBLE    Array[972, 972]
   PPR             DOUBLE    Array[3, 972, 972]
   IONIZ           DOUBLE    Array[3, 972, 972]
   RR              DOUBLE    Array[3, 972, 972]
   AI              DOUBLE    Array[972, 972]
   DC              DOUBLE    Array[3, 972, 972]
   DR              DOUBLE    Array[3, 972, 972]

6.6  The two-ion model developed for version 9

6.7  Contribution functions

6.8  The stellar case - irradiances and volume DEM

6.9  Definitions for emission measure analysis

6.10  Non-Maxwellian particle distributions

6.11  Photoexcitation and Stimulated Emission

6.11.1  Implementation of Photoexcitation and Stimulated Emission

6.12  Photoexcitation by arbitrary radiation fields

6.13  Ionization and recombination

6.14  Continuum calculations

6.14.1  Two photon continuum

6.14.2  Bremsstrahlung

6.14.3  Free-bound continuum

7  Some examples on how to use the software

7.1  Calculating line intensities.

 IDL >ch_ss

IDL> ch_synthetic, wmin, wmax, output=output, err_msg=err_msg, msg=msg, $
      pressure=pressure, density=density, $
      model_file=model_file, all=all,sngl_ion=sngl_ion, $
      photons=photons,  masterlist=masterlist,  $
      save_file=save_file , verbose=verbose,$
      logt_isothermal=logt_isothermal,  logem_isothermal=logem_isothermal,$
      goft=goft, ioneq_name=ioneq_name, dem_name=dem_name, $
      noprot=noprot, rphot=rphot, radtemp=radtemp, progress=progress

• 	Wmin, Wmax:   minimum  maximum of the desired wavelength range in Angstroms
  
  
• The (Te,Ne) model for the calculation:

         Pressure:  pressure in emitting region (Pe,  cm^-3 K). 
                    Only a single value is accepted, and the calculation is
                    performed at constant pressure.
  
         Density:   density in emitting region (Ne, cm^-3). 
                    Only a single value is accepted, and the calculation is
                    performed at constant  density, unless LOGT_ISOTHERMAL is
                    defined. In this case, DENSITY can be an array of values, but
                    has to have the same number of elements as LOGT_ISOTHERMAL.
  
  
         model_file    Full path of the (Te,Ne) file if defined. 
                       This file should have two columns, one with the Te (K)
                       values, and one with the Ne (cm^-3) values. If these
                       values are not sorted in ascending order of Te, the
                       routine does sort them.
  
  
• IONEQ_NAME: The ionization fraction file to be used. The program will prompt the user to select one if not defined.
• OUTPUT: The name of the structure containing the line intensities and details.

LOGT_ISOTHERMAL:   Array of logarithmic temperatures.
LOGEM_ISOTHERMAL:  Array of logarithmic emission measures (0 by default).

  IDL> ch_synthetic, 10,20., output=str , pressure=1.e+15,$
      ioneq_name=!ioneq_file,$
         dem_name=concat_dir(concat_dir(!xuvtop,'dem'),'flare.dem'),$
         /photons, /noprot, /all, sngl_ion=['fe_17','fe_18']

IDL> help, str,/st
IDL> help, str.lines[0],/st

7.2  Saving, restoring and exporting the CHIANTI line intensities structure

1. as IDL binary files using the SolarSoft routines:

   IDL> savegen, file='ch_int_10_20_fe.genx', struct=str
   IDL> restgen, file='ch_int_10_20_fe.genx', struct=str
   
   

   to save and restore the IDL structure str in the file ch_int_10_20_fe.genx.
   Please note that we discourage the use of e.g.:

   IDL> save, file='output.save', output
   IDL> restore, file='output.save'
   
   

   since IDL save files generated with later versions of IDL are usually not readable with earlier versions.
2. as FITS binary tables, that can be easily exported and read by different platforms. We have written two IDL routines:

   IDL> ch_write_fits, str, 'output.fits'
   IDL> ch_read_fits,'output.fits', str
   
   

   to save and restore the IDL structure str in the FITS file output.fits. Aside from an introductory HEADER, the contents of the IDL structure are converted into two binary tables. Extensive comments are added.

7.3  Create a latex or ascii file with all the line details

 IDL> ch_ss

 IDL> ch_line_list, transitions, outname, latex=latex, ascii=ascii, $
      wmin=wmin,wmax=wmax,$
      SPECTRUM=SPECTRUM, abundfile=abundfile, min_abund=min_abund, $
      minI=minI,photons=photons,kev=kev, $
      all=all,no_sort=no_sort, sngl_ion=sngl_ion

IDL> restgen, file='ch_int_10_20_fe.genx', struct=tran
IDL> ch_line_list, tran, 'ch_line_list.tex', /latex,$
     abundfile=concat_dir(concat_dir(!xuvtop,'abundance'),'cosmic.abund'),$
     mini=1e13

unix> latex ch_line_list
unix> latex ch_line_list
unix> latex ch_line_list
unix> xdvi ch_line_list

 IDL > latex_wvl_dem,100.,200., pressure=1.e+15,mini=1. 

IDL> restgen, file='ch_int_10_20_fe.genx', struct=tran
IDL> ch_line_list, tran, 'ch_line_list.ascii', /ascii,$
     abundfile=concat_dir(concat_dir(!xuvtop,'abundance'),'allen.abund'),$
     mini=1e13

 IDL > ascii_wvl_dem,100.,200.,pressure=1.e+15,mini=1. 

7.4  Calculating continuum intensities

freefree,5.e+6,findgen(50)+1.,ff 
freebound,5.e+6,findgen(50)+1.,fb
two_photon,5.e+6,findgen(50)+1.,tp

window,0 
plot,findgen(50)+1.,ff+fb+tp,xtit='Wavelength (A)'
oplot, findgen(50)+1.,ff,line=2
oplot, findgen(50)+1.,fb,line=3
oplot, findgen(50)+1.,tp,line=4

7.5  Creating a synthetic spectrum with the continuum

IDL> make_chianti_spec, TRANSITIONS, LAMBDA, OUTPUT, BIN_SIZE=BIN_SIZE,  $
        INSTR_FWHM=INSTR_FWHM,  BINSIZE=BINSIZE, $ 
        WRANGE=WRANGE, ALL=ALL, continuum=continuum, $
        ABUND_NAME=ABUND_NAME, MIN_ABUND=MIN_ABUND, $
        photons=photons, file_effarea=file_effarea, $
        err_msg=err_msg,  verbose=verbose

IDL> restgen, file='ch_int_10_20_fe.genx', struct=tran
IDL> make_chianti_spec, tran, lambda, struct,/CONTINUUM, $
     BIN_SIZE=0.01, instr_fwhm=0.1,  WRANGE=[10.,19.],$
      abund_name=concat_dir(concat_dir(!xuvtop,'abundance'),'cosmic.abund')

IDL> help, struct,/st
IDL> help, struct.lines[0],/st

IDL> window,0 & plot,struct.lambda,struct.spectrum
      for i=0,n_elements(struct.lines) -1 do $
     if struct.lines[i].peak gt 7e5 then $
   xyouts, struct.lines[i].wvl,  struct.lines[i].peak, struct.lines[i].snote 

IDL> savegen, file='ch_spectrum_10_20_fe.genx', struct=struct
IDL> ch_write_fits, struct, 'ch_spectrum_10_20_fe.fits'

 IDL > synthetic, 150., 200., 1., pressure=1.e+15, wvl, spectrum, list_wvl, list_ident

 IDL > synthetic_plot, wvl, spectrum, list_wvl, list_ident, 2.

7.5.1  Create a spectrum in the isothermal approximation

 IDL >ch_ss

 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.

7.6  The user-friendly multi-purpose widget ch_ss.pro

       IDL> ch_ss, font=font

7.6.1  SECTION 1 - The Calculation of the CHIANTI line intensities.

• - Minimum and maximum wavelengths in Angstroms
• - The model used for the calculation. Three are the options: 1) a constant density (cm⁻³) 2) a constant pressure (cm⁻3 K) 3) a general (Te,Ne) model. In this case, a file will be read. This file should have two columns, one with the Te (K) values, and one with the Ne (cm⁻³) values.
• - The ionization fraction file to be used. "*.ioneq" files can be selected from either the CHIANTI database, the working directory or selected via a widget.
• - All ions ? If set to yes (default), then all the ions present in the database will be included.
  If set to no, then it is possible to select a list of ions with a widget
• - All lines ? If set to no (default), only the lines for which there are observed energy levels are included
  If set to yes, also the lines that do not have corresponding observed energy levels are included. In this case, the wavelengths are calculated from the theoretical energy levels, and might not be very accurate.
• - Isothermal ? If set to no (default), a DEM file must be selected. "*.dem" files (i.e. files with a .dem extension) can be selected from either the CHIANTI database, the working directory or selected via a widget.
  If set to yes, then the user is requested to enter one or more temperatures (as logarithmic values - Log T ) and correspondent column emission measures EM logarithmic values. NOTE: if more than one value is entered, then the sequence must be separated by commas (e.g.: 6.0, 6.5, 7.), and both Log T and Log EM must have the same number of values
• - Photoexcitation ? If set to yes, you have to define: Trad: The blackbody radiation field temperature R/Ro: Distance from the centre of the star in stellar radius units
• - Units: Photons or Ergs
• - Protons: If set to Yes, the proton data are used to calculate the level population

7.6.2  SECTION 2 - calculation of a synthetic spectrum

• -Minimum and maximum wavelengths.
• -spectrum bin size in Angstroms in Angstroms. Disallowed if an Effective area file is used.
• -instrumental FWHM: Setting this to a non-zero value broadens each of the spectral lines with a Gaussian of the specified FWHM (in Angstroms) so mimicking the effects of instrumental broadening.
• -continuum: Add continua to the binned spectrum: free-free, free-bound and two-photon. Please note that the continuum calculation takes some time and you may want to define a minimum abundance value to speed the calculations.
• - All lines ? If set to no (default), only the lines for which there are observed energy levels are included. If set to yes, the ünobserved lines" will be added, but only if they are present in the structure.
• -elemental abundances: "*.abund" files (i.e. files with a .abund extension) can be selected either from the CHIANTI database, the working directory, or via a widget.
• -select a minimum abundance value: If set not null, only the lines of those elements which have an abundance greater than the value set are selected. Also, the continuum is calculated only for those elements which have an abundance greater than the value set. This can significantly speed up the calculations. By default, the minimum value in the selected abundance file is used.
• Eff. Area: (Yes/No): If you want to fold the spectrum with an effective area. If set to Yes, you are requested to choose an input ascii file with two columns, the wavelength and the effective area values (cm²). The spectrum is multiplied with these values. the wavelenghts in the file (that might not be linear) are used to create the spectrum. Note that this option only works well if a sufficient number of bins is given. The line intensities contributing to each bin are summed, and subsequently convolved with a gaussian of full-width-half-maximum FWHM, if FWHM is not set = 0. Please note that the convolution might not work if a small number of bins is defined.
  Also note that to have the correct output units (counts s-1 bin-1) the appropriately scaled DEM (or EM) values must be provided.

7.6.3  SECTION 3 - selection of parameters for plotting and output

• Labels ? : Setting this to yes plots a vertical line for each spectral line in the spectrum, and also writes a label above the strongest lines indicating the ion from which the line arises.
• Min.: Only lines which have an intensity greater than the value set here will be listed and, if requested, labelled and selected for inclusion in the various outputs. Setting the value=0. will result in all lines being listed and written in the outputs.
• X,Y, XOOM, UNZOOM: It si possible to select a region of the spectrum, by zooming with the use of the mouse or by setting the X,Y ranges.
  NOTE that only the line details and portion of the spectrum shown will be output.
• LINEAR/LOG To plot the spectrum in linear or log scale
• Create PS file: A postscript file is created.
• Hardcopy: the postscript file ïdl.ps" is created and sent to the default printer.
• Save Line details (latex): The details of the lines shown in the plot will be saved in a latex file.
• Save Line details (ascii): The details of the lines shown in the plot will be saved in an ascii file.
• Save Spectrum (ascii): The X,Y values of the spectrum are saved in an ascii file.
• Save Spectrum (IDL/FITS): The details of all the lines and the arrays of the X,Y values of the spectrum are saved into an IDL or FITS file.

7.7  Photoexcitation from any user-provided radiation field

FUNCTION o6_lines, lambda, a

;   Vernazza & Reeves (1978) give the quiet Sun O VI 1032 flux to be
;   305.28 erg/cm2/sr/s. The 1038 line is blended with C II, so I take
;   it to be half of the 1032 line. I assume the FWHMs of the lines are
;   0.2 angstroms.
;
;   A   Velocity (km/s) relative to emitting ions of the structure emitting
;       the radiation field. A positive velocity implies a redshift.

IF n_elements(a) EQ 0 THEN a=0.

siz=size(lambda)
spectrum=dblarr(siz[1],siz[2])

cc=2.998d5   ; speed of light, km/s

p1=305.28/0.2
p2=p1/2.

c1=1031.914
c1=c1+ (a/cc * c1)
;
c2=1037.615
c2=c2+ (a/cc * c2)
w=0.2/2.35

i=where(abs(lambda-c1) LE 6.*w)
IF i[0] NE -1 THEN spectrum[i]=p1*exp(-(lambda[i]-c1)^2/2./w^2)*4.*!pi/2.998d10

i=where(abs(lambda-c2) LE 6.*w)
IF i[0] NE -1 THEN spectrum[i]=spectrum[i]+p2*exp(-(lambda[i]-c2)^2/2./w^2)*4.*!
pi/2.998d10

return,spectrum
END

IDL> show_pops,8,6,radfunc='o6_lines, 20',rphot=1.1

v=findgen(11)*10.
for i=0,10 do begin
  radfunc_string='o6_lines, '+trim(v[i])
  show_pops,8,6,radfunc=radfunc_string,rphot=1.1
endfor

function udens_bb, lambda

t=6d3    ; temperature of Sun, 6000 K
ee=1.439d8/lambda/t

result=8.*!pi*1.986d-8/lambda^2*(1d8^3)/lambda^3/((exp(ee)-1))
return,result

END

IDL> show_pops,8,6,radfunc='udens_bb',rphot=1.1

IDL> show_pops,8,6,radtemp=6000.,rphot=1.1

7.8  Non-maxwellian distribution of electron velocities

IDL> em=emiss_calc(8,6,temp=[5.5,6.0],sum_mwl_coeff=[0.75,0.25],dens=9.0)
IDL> em150=em[40].em
IDL> em173=em[43].em
IDL> em1032=em[77].em
IDL> print,em150/em1032,em173/em1032
     0.030072876
     0.043500302

IDL> show_pops,8,6,lev=-8

Log10 density:      10.0
Log10 temperature:   5.5

  1           1s2.2s 2S1/2  1.00e-00
  2           1s2.2p 2P1/2  2.30e-07
  3           1s2.2p 2P3/2  4.52e-07
  4           1s2.3s 2S1/2  5.07e-11
  5           1s2.3p 2P1/2  7.26e-12
  6           1s2.3p 2P3/2  1.44e-11
  7           1s2.3d 2D3/2  5.30e-12
  8           1s2.3d 2D5/2  7.96e-12

IDL> show_pops,8,6,lev=-8,temp=[5.5,6.0],sum_mwl_coeffs=[0.75,0.25]

Log10 density:      10.0
Using a sum of Maxwellians

  1           1s2.2s 2S1/2  1.00e-00
  2           1s2.2p 2P1/2  2.26e-07
  3           1s2.2p 2P3/2  4.43e-07
  4           1s2.3s 2S1/2  8.93e-11
  5           1s2.3p 2P1/2  1.60e-11
  6           1s2.3p 2P3/2  3.16e-11
  7           1s2.3d 2D3/2  1.13e-11
  8           1s2.3d 2D5/2  1.69e-11

7.9  Looking at level populations

7.9.1  plot_populations

 IDL > plot_populations,'si_3',3.e+4,4 

7.9.2  ch_pops routine

IDL> pop=ch_pops('fe_13')

   DENS            DOUBLE       1.0000000e+10
   TEMP            DOUBLE           1778279.4
   LEVEL           STRUCT    -> <Anonymous> Array[749]
   RADTEMP         FLOAT          -1.00000
   RPHOT           FLOAT          -1.00000
   PROTON          STRING    'yes'
   VERSION         STRING    'CHIANTI 8.0.2'
   DATE            STRING    'Wed Jun 28 15:36:26 2017'
   SUM_MWL         INT              0
   SUM_MWL_COEFFS  FLOAT          -1.00000

   INDEX           INT              1
   TERM            STRING    '3s2 3p2 3P0'
   POP             DOUBLE          0.11817674

7.9.3  get_populations

IDL> get_populations,'fe_13', 1e6, output='fe_13_pop'

7.9.4  pop_plot

    pop_plot,26,13,wrange=[200,205]

    pop_plot,26,13,wrange=[330,370]

7.9.5  Looking at the processes that populate each level

 IDL> pop_processes,'fe_13',lev=4

Level:   3s2.3p2 1D2                   

Log10 Temperature:   6.2
Log10 Density:      10.0

Population leaving level 4
  rad. decay:     1.60e+01     42.50%
  e de-exc:       3.29e-01      0.87%
  e exc:          2.10e+01     55.88%
  p de-exc:       2.44e-01      0.65%
  p exc:          3.75e-02      0.10%
  stim. emiss:    0.00e+00      0.00%
  photoexc:       0.00e+00      0.00%
                  --------
           TOTAL  3.77e+01


Population entering level 4
  rad. decay:     3.50e+01     92.98%
  e de-exc:       3.38e-02      0.09%
  e exc:          1.47e+00      3.92%
  p de-exc:       2.81e-03      0.01%
  p exc:          1.13e+00      3.01%
  stim. emiss:    0.00e+00      0.00%
  photoexc:       0.00e+00      0.00%
                  --------
           TOTAL  3.77e+01

7.10  Level lifetime

IDL> level_lifetime,'fe_13',4,lifetime
Level:     3s2.3p2 1S0
Lifetime (seconds):  9.098e-04

7.11  Metastable levels

IDL> metastable_levels, 'fe_13', meta
Metastable levels are: 
 1 3s2.3p2 3P0
 2 3s2.3p2 3P1
 3 3s2.3p2 3P2
 4 3s2.3p2 1D2
 5 3s2.3p2 1S0
 18 3s2.3p3d 3F4

7.12  Level energies

IDL> plot_config_energies, 'o_5'

7.13  Searching for a line

IDL> which_line,'o_6',1032

     Wavelength   i   j  Lower level           Upper level             A-value
*      1031.914   1   3  1s2.2s 2S1/2        - 1s2.2p 2P3/2           4.28e+08
       1037.615   1   2  1s2.2s 2S1/2        - 1s2.2p 2P1/2           4.21e+08

7.14  Ionization and recombination

IDL> cross = ioniz_cross(ion,energy [, z=, ion= ])

cross = ioniz_cross('h_1',[14.,20.]) 

IDL> rate = ioniz_rate(ion, temperature [, z= , ion =])

IDL> rate = ioniz_rate('fe_14',[1.e+6, 2.e+6]) 
or
IDL> rate = ioniz_rate('',[1.e+6, 2.e+6], z=26, ion=14)

IDL> rate = recomb_rate(ion, temperature [,z=, ion=])

IDL> rate = recomb_rate('fe_14',[1.e+6, 2.e+6])

IDL> make_ioneq_all, temperature, outname='new.ioneq'

7.15  Looking at the different ionisation equilibria

 IDL > plot_ioneq,'Mg'

 IDL > plot_ioneq,'Mg', ion=[8,10]

 IDL > print, max_temp ('Mg X')

7.16  Density and temperature diagnostics from line ratios

7.16.1  The DENS_PLOTTER and TEMP_PLOTTER widgets

 IDL > dens_plotter,'o_5'

 IDL > temp_plotter,'c_4'

7.16.2  The DENSITY_RATIOS procedure

 IDL > density_ratios,'o_5',1000.,1500.,8.,13.,den,rat,desc

 IDL >  print, desc 
 IDL > CHIANTI V. 4.0 O V 1371.2939 (Å)/1218.3929 (Å)  T = 2.51e+05 (K)

7.16.3  The TEMPERATURE_RATIOS procedure

 IDL >   temperature_ratios,'c_4',100.,1600.,4.,6.,temp,rat,desc

 IDL > print, desc
 IDL > CHIANTI V. 4.0 C IV 384.1750+384.1900 (Å)/1550.7750 (Å) Ne = 1.00e+10 (cm!e-3!n)

7.16.4  The CHIANTI_NE and CHIANTI_TE widgets

7.16.5  Calculating temperatures by using different ions

7.17  Calculating contribution functions

 IDL >  gofnt,'fe_24',250.,260.,temperature,g,desc  

7.17.1  g_of_t.pro

    result=g_of_t(26,13,dens=9.)
    result=g_of_t(26,13,wrange=[200,205],/abund)
    result=g_of_t(26,13,/no_de)

    result=g_of_t(26,13,dens=9.)
    ion_interp,t,result,ti,g_ti,10
    print,ti(where(g_ti eq max(g_ti)))

7.18  Calculating emissivities

    emiss=emiss_calc(26,13)

7.18.1  emiss_select.pro

emiss=emiss_calc(26,13)
em202=emiss_select(emiss,wra=[200,205],sel_ind=sel_ind)

7.19  Calculating radiative losses

 IDL > rad_loss,temperature,loss_rate

7.20  Emission measure analysis

7.20.1  integral_calc.pro

    integral_calc,26,13,wrange=[200,205],dens=9.

    integral_calc,26,14,wrange=[210,220],dens=9.

8  SDO/AIA temperature responses

AIA_RESP= ch_aia_resp('20100522', pressure=1e15, $
      abund_name=!xuvtop+'/abundance/sun_coronal_1992_feldman_ext.abund',$ 
      ioneq_name=!xuvtop+'/ioneq/chianti.ioneq')

9  The calculation of the DEM

• the file with the observed line intensities. It can be selected using a widget-type browse from within CHIANTI_DEM or using the optional keyword FILE_INPUT='myfilename' . It must contain 5 columns of unformatted data (separated by at least one space). The 5 fields are:
  1) the observed wavelength λ_obs [Å].
  2) The observed intensity I_obs.
  3) The corresponding uncertainty σ_obs on the intensity.
  Note: by default the intensity units are ergs  cm⁻² s⁻¹ sr⁻¹. However, via the /phot keyword, they can be phot  cm⁻² s⁻¹ sr⁻¹, or with both the /phot and /arcsec keywords, they can be phot  cm⁻² s⁻¹ arcsec⁻¹.
  4) The value of δλ [Å]. All the theoretical lines that may have contributed to the observed lines, i.e. that have a theoretical wavelength λ_theo in a λ_obs ±δλ range will be searched for. This value should correspond to the spectral resolution of the instrument at that wavelength.
  5) The identification, written as a string of up to 20 characters. For example:
  171.114 4811.0 1443.0 0.25 Fe IX
  174.604 4005.0 1202.0 0.25 Fe X
  180.448 3877.0 1163.0 0.25 Fe XI bl Fe X
  195.149 3443.0 1033.0 0.25 Fe XII
• the constant pressure N_e T  [cm⁻³ K] or the constant density N_e  [cm⁻³], for which the contribution functions will be calculated, passed to the routine as a keyword.
• the ionization equilibrium file, selected using a widget.
• the elemental abundances file. A selection of files are already stored in the CHIANTI package, but user-defined files in the working directory can also be used. Any *.abund file present in the CHIANTI database or in the working directory can be selected through a widget from within CHIANTI_DEM. The selected file can also be edited, to change the abundances of any element.
• An output file name must also be supplied via a keyword (e.g. OUTPUT= 'active_region'). Various files will be generated by CHIANTI_DEM having file names created by adding suffixes to the output file name.

• FILE_INPUT: optional; if not set, you are prompted to select the observation file using a widget-type search.
• ARCSEC: optional set this if the intensities are specified in units per arcsec⁻².
  The default units are ergs  cm⁻² s⁻¹ sr⁻¹.
• PHOT: optional; set this if the intensities are specified in units per steradians⁻¹.
  The default units are ergs  cm⁻² s⁻¹ sr⁻¹.
• OUTPUT : required; the name for the output. Suffixes will be added to this name when creating the various outputs.
• FILE_GT: if not set, the routine GET_CONTRIBUTIONS is called. Either the pressure or the density must be set in this case.
  If set, it has to specify the name of the file previously created by GET_CONTRIBUTIONS, where all the contribution functions C(T) are stored.
• PRESSURE: the value of the pressure (Ne T). Required if you do not already have the contribution functions C(T) (i.e. if you do not set FILE_GT). Either the pressure or the density must be set in this case.
• DENSITY : the value of the electron density (Ne). Required if you do NOT already have the contribution functions C(T). Either the pressure or the density must be set in this case.
• CUT_GT: optional; if set, only those theoretical lines that have a MAX(C(T)) greater than the value set, are kept; it is useful to set this value in order to reduce the number of lines in the file where the C(T) are stored. If not set, a default value of 10⁻³⁰ is adopted.
• N_MATCHES: optional; in the unlikely event that more than 100 (default value for N_MATCHES) theoretical lines corresponding to an observed line are found, the routine stops. In this case, you have to start again setting N_MATCHES equal to a greater number.
• PLOT_GT: optional; if set, plots of the G(T) of the theoretical lines contributing to each observed line not excluded are created. It is possible to change the scale and create postscript files of these plots, interactively.
• EXCLUDE_OBS_WVL: optional; if set, has to be an array that specifies the wavelengths of the lines that you want to exclude from the fit. Note that even if you set this keyword and run GET_CONTRIBUTIONS all the theoretical lines found corresponding to all the lines in the input file are written in the C(T) file. It is only in the fit that the lines are excluded.
• DEM_FILE: optional; if set you are prompted to choose a DEM file to be used initially, instead of the default constant value of 10²². You can either choose one of the files in the CHIANTI database or any you have in the working directory. A plot of the DEM is created. The values in the file are marked as crosses, the mesh points are marked with triangles.
• QUIET: optional. Set to avoid various messages and the details of the result.

9.1  Default option: MPFIT_DEM

 MIN_logT:   minimum temperature (log T) for the DEM
              calculation  
 MAX_logT:   maximum temperature (log T) for the DEM
              calculation  
 DT_logT:      temperature step (log T) for the DEM
              calculation (default=0.1)

SPL_LOGT:    logt T values for the spline nodes. Note
             that the number should not be larger than the number of
             input lines -1.

SPL_LOGDEM:  log DEM input values. If not defined, a
             value of 20 will be used.

MIN_LIMITS
MAX_LIMITS:  minimum and maximum limits for
             the log DEM values at the spline temperatures.

  1) output+'_xrt_dem.dem': the DEM as a CHIANTI ascii file.
  2) output+'.out'         : an ascii file with the predicted intensities
  3) output+'_xrt_dem.save': an IDL save file with:

  input: the input structure used for the fitting
  logT_out: the log T
  log_dem_out: the log DEM 
  log_dem_mciter: (optional) the results of the Monte Carlo runs

	IDL> chianti_dem,output='test_obs',file_input='test_obs',$
	   pressure=1.e15,cut_gt=1e-30,/plot_gt

	IDL> chianti_dem,output='test',file_input='test_obs',$
	file_gt='test_obs.contributions', min_logt=5.5, max_logt=6.6

restore, file='test_xrt_dem.save',/ver

      x_min=min(logT_out)
      x_max=max(logT_out)
      y_min=min(log_dem_out)
      y_max=max(log_dem_out)

     plot,  logT_out, log_dem_out,$
             xr=[x_min,x_max],yr=[y_min,y_max],$
             xstyle=1,xtitle = ' log Teff [ !eo!nK ]',$
             ytitle ='log DEM [ cm!S!E-5 !NK!S!E-1!N ] ',$
             title='XRT DEM INVERSION TECHNIQUE'

; over-plot the  observed/expected ratio * DEM at the effective temperature:

n_obs=n_elements(obs_int)

for iobs=0,n_obs-1 do begin
         
         point=spline(logT_out, log_dem_out), alog10(t_eff[iobs]))

         oplot, alog10(t_eff[iobs]), alog10(obs_int[iobs]/exp_int[iobs]* 10.^point), psym=6

         xyouts, alog10(t_eff[iobs]), alog10(obs_int[iobs]/exp_int[iobs]*$
                                             10.^point[iobs]), $
                 ' '+strtrim(obs_id[iobs],2), charsize=0.8, Orientation=90

endfor

; plot the  observed/expected ratio * DEM at the temperature of the maximum of the G(T):

      plot,  logT_out, log_dem_out,$
             xr=[x_min,x_max],yr=[y_min,y_max],$
             xstyle=1,xtitle = ' log Tmax [ !eo!nK ]',$
             ytitle ='log DEM [ cm!S!E-5 !NK!S!E-1!N ] ',$
             title='XRT DEM INVERSION TECHNIQUE'

for iobs=0,n_obs-1 do begin
         
         point[iobs]=spline(logT_out, log_dem_out), temp_max_tot_contr[iobs])

         oplot, [temp_max_tot_contr[iobs]], [alog10(obs_int[iobs]/exp_int[iobs]* 10.^point)], psym=6

         xyouts, temp_max_tot_contr[iobs], alog10(obs_int[iobs]/exp_int[iobs]*$
                                             10.^point[iobs]), $
                 ' '+strtrim(obs_id[iobs],2), charsize=0.8, Orientation=90

endfor

; if you have run the  XRT_DEM Monte Carlo simulations and want to plot them 
; again, do:

restore, file='test_xrt_dem.save',/ver
sz=size(log_dem_mciter)
MC_iter=sz[2]

plot, logT_out,log_dem_out, psym=10,th=th, col=0,$
       xr=[x_min,x_max],yr=[y_min,y_max],$
             xstyle=1,xtitle = ' log T [ !eo!nK ]',$
             ytitle ='log DEM [ cm!S!E-5 !NK!S!E-1!N ] ',ystyle=1,$
      title='XRT DEM INVERSION TECHNIQUE'

  for ii=0, MC_iter-1 do oplot, logT_out, log_dem_mciter[*,ii], th=th, col=100, psym=10
  oplot, logT_out,log_dem_out, psym=10,th=th, col=0
        

9.2  DATA2DEM_REG

  INPUT:

  DO_DEMREG: keyword to ask the routine to run
             DATA2DEM_REG. 
  DEMREG_LOGT_MIN: minimum temperature (log T) for the
                   DEM calculation 
  DEMREG_LOGT_MAX: maximum temperature (log T) for the
                   DEM calculation 
  NT_DEMREG: Number of temperatures  for the DEM
             calculation (default=20). Note that this
             number must be larger than the number of
             input lines+1.

  OUTPUT:

   1) output+'_demreg.dem': the DEM as a CHIANTI ascii 
   file.

   2) output+'_demreg.save': an IDL save file with 
   REG: a structure containing all the input and output
   results of the routine.

EXAMPLE:

               IDL> chianti_dem,output='test',file_input='test_obs',$
               file_gt='test.contributions',/do_demreg,demreg_logt_min=5.5,$ 
               demreg_logt_max=6.6, nt_demreg=20 

restore, file='test_demreg.save'

     x_min=min(reg.logt)
      x_max=max(reg.logt)
      y_min=2d19
      y_max=2d23

      ploterr,reg.logt,reg.dem_pos,reg.elogt_pos,reg.edem_pos,$
              /nohat,errcolor=9,  xr=[x_min,x_max],yr=[y_min,y_max],$
             xstyle=17,ystyle=17,/ylog, title='Regularized DEM', $
              xtitle='log!D10!N T',ytitle='DEM(T) [cm!U-5!N K!U-1!N]'

9.3  MCMC_DEM

  INPUT:

  DO_MCMC: keyword to ask the routine to run MCMC
     
  MCMC_LOGT_MIN: minimum temperature (log T) for the
                   DEM calculation 
  MCMC_LOGT_MAX: maximum temperature (log T) for the
                   DEM calculation
  MCMC_LOGT_STEP:  temperature step (log T) for the DEM
               calculation (default=0.1)

  OUTPUT:

  1) output+'_mcmc.dem': the DEM as a CHIANTI ascii file.

  2) output+'mcmc.save' an IDL save file with all the
  input and output results, keyword parameters, etc.

Example:

 chianti_dem,output='test',file_input='test_obs',$
               file_gt='test.contributions', /do_mcmc, mcmc_logt_step=0.1,$
               mcmc_logt_max=6.6, mcmc_logt_min=5.5

 x_min=min(logt_grid)
      x_max=max(logt_grid)
      y_min=min(alog10(dem_out))
      y_max=max(alog10(dem_out))

 plot,  logt_grid, alog10(dem_out),$
                xr=[x_min,x_max],yr=[y_min,y_max],$
                xstyle=1,xtitle = ' log Teff [ !eo!nK ]',$
                ytitle ='log DEM [ cm!S!E-5 !NK!S!E-1!N ] ',$
                title='MCMC DEM INVERSION TECHNIQUE', psym=10


        for iobs=0,n_elements(obs_int)-1 do begin         &$   
            point=spline(logt_grid, alog10(dem_out), alog10(t_eff[iobs]))  &$          
         oplot, [alog10(t_eff[iobs])], [alog10(obs_int[iobs]/exp_int[iobs]* 10.^point)], psym=6 &$        
    xyouts, alog10(t_eff[iobs]), alog10(obs_int[iobs]/exp_int[iobs]*10.^point), $
                    ' '+strtrim(obs_id[iobs],2), charsize=0.8, Orientation=90 &$
 end 

9.4  Examples

IDL > CHIANTI_DEM,OUTPUT='test',FILE_INPUT='test_obs',PRESSURE=1e16,/PLOT_GT

9.5  Some final remarks

10  The CHIANTI line intensities structure

       .lines     A structure containing information about the lines. 
                  Its size is the number of lines in the spectrum. The 
                  tags are:

                  .iz     The atomic number of the elements (e.g., 26=Fe)

                  .ion    The ionisation stage (e.g., 13=XIII)

                  .snote  The identification of the ion (e.g., 'Fe XXIV d')

                  .ident  The identification of the transition, configuration
                           and terms in text form.

                  .ident_latex
                          The identification of the transition, configuration
                           and terms in latex form.

                  .lvl1   The lower level of the transition (see .elvlc 
                          file for ion)

                  .lvl2   The upper level for transition.

                  .tmax   The temperature of maximum emission of the line.

                          If the G(T) are output, tmax is the maximum of G(T).

                          If the isothermal approximation is used  tmax=0.

                          If a DEM is used,  tmax is the maximum of the 
                          emissivity that includes the product of the ion
                          fraction and the DEM.
                          Rounded to nearest 0.1

                  .wvl    Wavelength of the transition, in Angstroms.

                  .flag   A flag, =-1 if the line has only theoretical energy
                          levels. Otherwise flag=0.

                  .int    Intensity of line (erg/cm2/s/sr or phot/cm2/s/sr), 
                          divided by the element abundance (exclusive with .goft). 

                  .goft   The G(T) of the line (optional /exclusive with .int).


       .ioneq_name     The ion balance file used (full path).
       .ioneq_logt        The Log10 T values associated.
       .ioneq_ref      The references.

       .dem_name       The differential emission measure file eventually  used
                       (full path).
       .dem            The Log10 DEM values 
       .dem_logt          The Log10 T values associated.
       .dem_ref        The references.

       .model_name    A string indicating the model used: 

                    1- Constant density
                    2- Constant pressure
                    3- Function (Te,Ne)

       .model_file    Full path of the (Te,Ne) file if defined. Null string otherwise.

       .model_ne    the Ne value(s).

                     - a scalar if 'Constant density' is selected.
                     - an array if 'Function' is selected.
                     - 0. if constant pressure is selected.

       .model_pe    the Pe value.

                     - a scalar if constant pressure is selected.
                     - 0. if 'Constant density' is selected.
                     - an array=density*temperature if 'Function' is selected.
                          
       .model_te    the Te values if 'Function' is selected. Otherwise 0.

       .wvl_units  The wavelength units.

       .wvl_limits    The wavelength limits specified by the user.

       .int_units  The intensity units (erg/cm2/s/sr or phot/cm2/s/sr) if
                  intensities are calculated, otherwise the G(T) units 
                  (erg cm3/s/sr or phot cm3 /s/sr)

       .logt_isothermal
                  The Log10(T) values used. 

       .logem_isothermal
                  The Log10(EM) values used. 

       .date      The date and time when the structure was created.

       .version   The version number of the CHIANTI database used.

       .add_protons 
                  A flag (0/1) to indicate whether proton data were used (1)
                  or not (0) to calculate the level population.

       .photoexcitation
                  A flag (0/1) to indicate if photoexcitation was included (1)
                  or not (0).

       .radtemp 
                 The blackbody radiation field temperature used (if
                 photoexcitation was included).

       .rphot
              Distance from the centre of the star in stellar radius units  
              (if photoexcitation was included).

11  The CHIANTI spectrum structure

                     LAMBDA      The array of X-values
                     SPECTRUM    The array of Y-values
                     UNITS       The units of LAMBDA, SPECTRUM
                     WRANGE      The wavelength range
                     INSTR_FWHM  The Instrumental FWHM
                     BIN_SIZE    Width of the Bins  (fixed) in angstroms
                     ABUND_NAME  The CHIANTI abundance file name             
                     ABUND       The abundance values
                     MIN_ABUND   The minimum abundance value used                 
                     ABUND_REF   The references
                     CONTINUUM   The values of the continuum (if calculated)                 
                     FILE_EFFAREA The Effective Area File used (optional)
                     EFFAREA       The array of effective area values
                                   (optional - same size of LAMBDA)

                    .LINES      An array of structures, for all the lines used               
                                to calculate the SPECTRUM. 
                                The tags are the same as those created by 
                                CH_SYNTHETIC, plus
                       .PEAK    The peak intensity of the line in the spectrum
                                (approx. value) 

12  References

References

[ ]

N. R. Badnell. Radiative Recombination Data for Modeling Dynamic Finite-Density Plasmas. ApJS, 167:334-342, December 2006.

[ ]

G. Del Zanna and H. E. Mason. Xuv spectroscopy. Living Reviews in Solar Physics, 15, 2018.

[ ]

K. P. Dere. Ionization rate coefficients for the elements hydrogen through zinc. A&A, 466:771-792, May 2007.

[ ]

M. F. Gu. Indirect X-Ray Line-Formation Processes in Iron L-Shell Ions. ApJ, 582:1241-1250, January 2003.

[ ]

C. Jordan and R. Wilson. ASSL Vol. 27: Physics of the Solar Corona, page 219, 1971.

[ ]

E. Landi, G. Del Zanna, P. R. Young, K. P. Dere, H. E. Mason, and M. Landini. CHIANTI-An Atomic Database for Emission Lines. VII. New Data for X-Rays and Other Improvements. ApJS, 162:261-280, January 2006.

[ ]

S.~R. Pottasch. On the interpretation of the solar ultraviolet emission line spectrum. Space Sci. Rev., 3:816, 1964.