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S. P. Catanzariti (Indiana State University), S. L. Keil (National Solar Observatory)
We compare changes in disk-integrated Ca-II K-line spectra with changes observed in full-disk K-line spectroheliograms. Disk-integrated K-line spectra have been obtained on a synoptic basis by the National Solar Observatory (NSO) at both its Kitt Peak and Sacramento Peak sites for the past two solar cycles. NSO also records Ca II K-line spectroheliograms on a daily basis at Sacramento Peak. The disk-integrated observations have been used as a proxy for changes in solar UV and EUV lines that can only be measured from space, as a predictor of satellite drag, to compare the Sun to other active and variable stars and to measure solar differential rotation on the Sun when viewed as a star. The goal of the comparison with the spectroheliograms is to understand and calibrate the causes of change in the disk-integrated spectra. For the past nine months, we have obtained the disk-integrated spectra and spectroheliograms simultaneously, using the Evans Facility to help eliminate sky transparency changes as a source of noise. We have also investigated several methods of normalizing the spectroheliograms before extracting plage area and brightness changes. Correlation between changes in the disk-integrated intensity and changes in the so-called emission index (an integral of the intensity over a one-angstrom band centered on the K-line) with changes in plage area and plage brightness integrated over the solar disk will be presented.
Funding for this project was provided by the National Science Foundation and the Air Force Office of Scientific Research.
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The author(s) of this abstract have provided an email address for comments about the abstract: catanzas@coral.indstate.edu; skeil@sunspot.noao.edu