This page (revision-16) was last changed on 11-Dec-2017 16:06 by Ignacio Ugarte-Urra

This page was created on 16-Jun-2010 22:23 by PeterYoung

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Spatial offset of intensity and velocity features
Spatial offset of intensity and velocity features

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At line 19 changed one line
A similar phenomenon was observed in SOHO/CDS data and was explained by [Haugan (1999)|http://adsabs.harvard.edu/abs/1999SoPh..185..275H] as being due to an "elliptical, tilted point spread function". This is illustrated in the plot below.
A similar phenomenon was observed in SOHO/CDS data and was explained by [Haugan (1999)|http://adsabs.harvard.edu/abs/1999SoPh..185..275H] as being due to an "elliptical, tilted point spread function (PSF)". This is illustrated in the plot below.
At line 23 changed one line
A point source imaged by EIS will yield an elliptical spot on the detector whose axes lie at an angle to the detector's axes. The spot will spread over a number of pixels on the detector and if Gaussian fits are performed at each pixel there will appear to be a blueshift on the north side of the spot and a redshift on the south side of the spot.
Such a PSF will yield an elliptical spot on the detector whose axes lie at an angle to the detector's axes. The spot will spread over a number of pixels on the detector and if Gaussian fits are performed at each pixel there will appear to be a blueshift on the north side of the spot and a redshift on the south side of the spot.
At line 25 added 2 lines
It is not clear yet if the EIS PSF has a tilted, ellipsoid shape like this but the velocity patterns observed suggest that it is similar. The shape would be expected to change along the slit and the thus the velocity patterns may vary with position within a raster.
At line 42 changed one line
When deriving velocities, the values obtained where the intensity peaks (in the case of bright points), or where the intensity is fairly uniform should be correct.
When deriving velocities, the values obtained where the intensity peaks (in the case of bright points), or where the intensity is fairly uniform should be correct. In particular, velocity results such as the outflows detected in active regions ([Harra et al. 2008|http://adsabs.harvard.edu/abs/2008ApJ...676L.147H,], [Doschek et al. 2008)|http://adsabs.harvard.edu/abs/2008ApJ...686.1362D,] will not be affected.
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The EIS team is investigating the PSF function and whether a software correction can be performed. The issue is complicated by the fact that the PSF probably changes shape along the slit.
The EIS team is investigating the PSF function and whether a software correction can be performed. Users are encouraged to look for the effect in their data and report their findings to their EIS team.
This page (revision-16) was last changed on 11-Dec-2017 16:06 by Ignacio Ugarte-UrraTop