This page (revision-7) was last changed on 18-Apr-2021 19:12 by PeterYoung

This page was created on 19-Nov-2009 17:16 by PeterYoung

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HeIIOffLimb
HeIIOffLimb

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At line 7 changed 6 lines
He II 256.317
He II 256.318
Si X 256.366
Fe X 256.398
Fe XII 256.410
Fe XIII 256.422
He II 256.317\\
He II 256.318\\
Si X 256.366\\
Fe X 256.398\\
Fe XII 256.410\\
Fe XIII 256.422\\
At line 16 changed one line
The off-limb spectrum being used is from 2007 March 9 20:03. Using the procedure outlined [elsewhere on the wiki|http://msslxr.mssl.ucl.ac.uk:8080/eiswiki/attach/DataProAnalysis/gauss_pixel_masks.pdf] a spatial region has been averaged to produce a single spectrum from which emission lines can be measured. Using standard density diagnostics we find the density is about 10<sup>8.5</sup>.
The off-limb spectrum being used is from 2007 March 9 20:03. Using the procedure outlined [elsewhere on the wiki|http://msslxr.mssl.ucl.ac.uk:8080/eiswiki/attach/DataProAnalysis/gauss_pixel_masks.pdf] a spatial region has been averaged to produce a single spectrum from which emission lines can be measured. Using standard density diagnostics we find the density is about 10^8.5.
At line 18 added 9 lines
!Fit to 256 feature
In the off-limb spectra, the feature at 256.3 is seen to comprise of two components that can be fit with two Gaussians. I find fit parameters of
256.321 0.071 37.1\\
256.413 0.106 139.2
(centroid, width and intensity, respectively). Based on the wavelengths above it seems, to first approximation, that the long wavelength Gaussian represents the coronal lines, and the short wavelength Gaussian the He II lines. Below we check the combined intensity of the four coronal lines.
At line 28 changed 2 lines
Fe X 257.296 122.8
Fe X 266.122 3.3
Fe X 257.296 122.8\\
Fe X 266.122 3.3\\
At line 42 changed one line
S X + Fe XII 259.527 56.0
S X + Fe XII 259.527 56.0\\
At line 64 added one line
This line can be estimated by making use of the stronger Fe XIII line at 251.96, however 256.42/251.96 is density sensitive. For the off-limb spectrum we know the density is low, and the 256.42/251.96 is actually relatively insensitive to density over 10^8 to 10^9, with a value of about 0.17. The 251.96 measured intensity is 69.0, and the so predicted 256.42 intensity is 11.7.
At line 66 added one line
!Summary
At line 68 added 3 lines
Combining the four estimated intensities gives a total of either 134.4 or 144.1, depending on which estimate of the Fe XII line intensity is used. These values are actually in very good agreement with the strength of the long wavelength Gaussian in the fit to the 256.3 feature mentioned above. This suggests that the method outlined above for estimating the intensities of the coronal lines actually works quite well.
__Caveat__ In estimating the intensities above, it was necessary to assume a low density of < 10^9 in order to apply some of the ratios. In particular, this was necessary for Fe X, XII and XIII. This method would need to be revised for, e.g., an active region observation.
This page (revision-7) was last changed on 18-Apr-2021 19:12 by PeterYoungTop