chianti_dem spline error

[Scott]

Hello,

Apologies, but I'm back with a new error. 

I purchased an official IDL license, and I'm using CHIANTI through SolarSoft. I am attempting to calculate a differential emission measure using chianti_dem (density=1e6) but I keep receiving the following error after it asks me if I would like to plot the EM loci curves (I decline, which is the default):

% Compiled module: SPLINE.
% SPLINE: X and Y must be arrays of 3 or more elements.

% Execution halted at: CHIANTI_DEM      1494 /home/sengle/ssw/packages/chianti/idl/dem/chianti_dem.pro
%                      $MAIN$           
% Program caused arithmetic error: Floating underflow
% Program caused arithmetic error: Floating overflow

Does this mean that it simply hasn't been able to fit the dem with a spline function, or is there an actual issue occurring? 

Here are the contents of the input file (emission line fluxes I'm using)

1199.55 27.0 5.4 0.5 N I
1411.9189 12.1 2.42 0.5 N I
1206.5551 279 4.46 0.5 Si III
1298.946 10.5 1.38 0.5 Si III
1238.821 83.7 1.79 0.5 N V
1242.804 44.7 1.4 0.5 N V
1358.512 81.5 2.16 0.5 O I
1393.755 156.0 3.32 0.5 Si IV
1402.77 82.2 3.08 0.5 Si IV
1401.163 16.0 2.68 0.5 O IV
1404.806 10.7 2.18 0.5 O IV
1407.384 4.37 2.24 0.5 O IV

and I selected the standard ioneq file, and the 2021_asplund abundance file. (Also, I had to modify get_abund_data.pro because it appears to be hardwired to look for the 2009 asplund abundance file.)

Best,

Scott

[G Del Zanna]

Scott,

apologies for the late answer, your email went into  my spam folder...

Thank you for spotting the problems.

I had a quick look and it seems my mistake in not defining the temperatures

of the spline nodes internally if nothing is given as input. 

You are right about the default abundance file which changed in v.10.1

I always run the routine with a minimum and max temperature range 

and a few spline nodes, and often with a range of max and min DEM values,

otherwise MPFIT usually fails.

I've tried 

chianti_dem, file_input='input',output='test',dens=1e6

and reproduced your errors.

If you try this 

chianti_dem, file_input='input',output='test',$

             file_gt='test.contributions',$

             spl_logt=[4.2,4.4,4.8,5.0,5.2,5.5,5.7],$            

             min_logt = 4.2, max_logt = 5.7

you get an answer. 

However, it would not be realistic, mainly because

1. neutral lines are very much wrong with the current CHIANTI version, even if they are optically thin.
2. many lines you have are from anomalous ions, so their EM is wrong; indeed if you plot the EM loci you can see it  yourself. 

We (me and Roger Dufresne) are in the process of including in CHIANTI more physical processes (mainly density and charge transfer) which improve 2), see e.g. our papers in the past few years. It may take just a few weeks/months to have a new version released.

In the mean time you could experiment with the improved ionization equilibria we have 

produced.

For 1) we'll need to include photo-ionisation which will take some more time. 

Giulio

---

From: chi...@googlegroups.com <chi...@googlegroups.com> on behalf of Scott <sgerar...@gmail.com>
Sent: 06 September 2023 18:05
To: chianti <chi...@googlegroups.com>
Subject: chianti_dem spline error

 

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