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Last modified: Tue Jan 4 12:52:37 2011.

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       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


       To compute the atomic data integral for use in column or volume
	emission measure work.


       Scientific analysis



	G(T) = 0.83 * Fr(T) * N_j * A_ji / N_e

	where Fr(T) is the ionisation fraction (e.g., from Arnaud & 
	Rothenflug), N_j the relative population of level j, A_ji the 
	A-value for the j->i transition and N_e the electron density. The 
	0.83 is the ratio of hydrogen to free electrons, which is constant 
	above around 10^4 K. This function is sharply-peaked at a 
	temperature T_mem (the temperature of maximum emission, which can 
	be different from the temperature of maximum ionisation, T_max) 
	and so an oft-used approximation is to take G(T) constant in the 
	range log T_mem - 0.15 to log T_mem + 0.15 and zero outside. The 
	value of the constant, which we call C_lambda here, is then given 

	C_lambda =    integral { G(T) dT }
                  T_mem * (10^0.15 - 10^-0.15)

	If EM(s) is the column emission measure, F the flux (erg cm-2 s-1)
	in a line lambda, Ab the abundance of the element and DE (erg) the
	energy for the transition, then:

	F = DE * Ab * C_lambda * EM(s)

	If we are dealing with intensities I (erg cm-2 s-1 sr-1) then:

	4pi * I = DE * Ab * C_lambda * EM(s)

	This program extracts the ionisation balance and emissivities from 
	the CHIANTI database and calculates C_lambda for all lines in the 
	specified wavelength interval WRANGE by integrating over 
	0.02 dex temperature intervals.

	The C_lambda functions for all the lines in the selected wavelength 
	range WRANGE are displayed as well as the temperature of maximum 
	emission (T_mem), DE*C_lambda and 4pi/(DE*C_lambda). These latter 
	two quantities are useful for the emission measure analysis.

	Any combination of the displayed lines can then be blended and the 
	corresponding quantities for the blend will be displayed.

	The function Fr(T) * N_j * A_ji can also be plotted at this stage.




	INTEGRAL_CALC, 26, 13, WRANGE=[200,205], /CHOOSE

	INTEGRAL_CALC, 14, 10, WRANGE=[250,270], DENS=10.


	IZ:	The atomic number of the ion
	ION:	The spectroscopic number of the ion (e.g., 12 = XII)


	DENS:	The density at which the emissivities are calculated 
	WRANGE: Wavelength range for which C_lambda functions are 
		calculated. If not given, then the 10 strongest lines 
		are printed.
	INDEX:	Particular elements in the emissivity structure can be 
		selected with INDEX. This allows integral_calc to be run 
		'silently'. The output is contained in the OUTSTR structure. 
		If index is given as, e.g., [7,8], then the C_lambda 
		functions for these two lines are summed and output.
	PATH:	Directly specify the directory path where the Chianti data 
		for the ion is found

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       RADTEMP  The blackbody radiation field temperature (default 
                6000 K).

       RPHOT    Distance from the centre of the star in stellar radius 
                units. I.e., RPHOT=1 corresponds to the star's surface. 
                (Default is infinity, i.e., no photoexcitation.)


	CHOOSE:	Allow ion balance calculations to be selected manually 
		(see choose_ioneq.pro routine).


	OUTSTR:	A structure with the following tags

		.tmem	- the T_mem for the line(s)
		.dec	- total( de * c_lambda )
		.pidec	- 4 * pi / total( de * c_lambda )

	Only output when INDEX is specified.






	Ver.1: PRY, 28-JUN-97.
	Ver.2: PRY, 7-OCT-97. Added TEMPI and GOFT, for plotting.
	Ver.3: PRY, 31-JUL-98. Added PATH.
	Ver.4: PRY, 6-APR-99. Added INDEX, OUTSTR. Removed TEMPI and GOFT 
		(these can be got from the g_of_t routine).
       Ver.5: PRY, 9-Dec-01. Modified for v.4 of CHIANTI.

       V.6, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V.7, 06-Aug-02 GDZ
              Changed the use of CHIANTI system variables. 

       V.8, 6-Feb-2006, Peter Young
              Integration is now performed on d(logT) intervals, rather than
              dT intervals following problems identified by Luca Teriaca.

 VERSION     :   8, 06-Feb-06

(See em/integral_calc.pro)