Thursday, July 31, 2014

First Look At IRIS Data

I've started a project to measure line positions, intensities, and ratios of the MgII h and k spectral lines coming from IRIS.  I've got a little way to go before I can start publishing these values, but here's a plot showing my progress:

Figure 1: MgII h spectral line spacial and temporal data

Now as you can see, it's a moderately complex plot.  The x-axis is the number of arc seconds from the center of the sun along the vertical axis of the sun.  The y-axis is the wavelength, in angstroms, of the spectral feature.

The data points themselves show at least three distinct features, all sort of in the center of the plot.  The three lines around 2803.5 angstroms are showing the position of the peak(s) and trough(s) in the MgII h line.  So as you move from left to right on the plot, you're moving from south to north on the surface of the sun.  As you move from bottom to top on the plot, you're looking at longer wavelengths.

The top "line" (follow the dots going from left to right) is it's peak position and is represented by the designation "h2r".  The middle "line" is "h3", and the bottom "line" is "h2v".  The line at the bottom of the plot is an artifact from the program I wrote to detect the peaks and troughs of the spectral features.

The red "lines" were data taken at about 16:33 UTC on 27 June 2014 and the green "lines" were taken about 5 minutes later at 16:38 UTC.  You can see that over that fairly short amount of time, the spectral features have changed pretty significantly.

Notice how the typical double peak goes away at -115 to -100.  Why?  It's looking at a sunspot at that location.  Why do these spectral features vanish when looking at a sunspot?

That's all I can say about this for now.  Much more to do to make this data presentable and usable to the astronomical community.

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