Solar Chromospheric Variability from the National Solar Observatory (NSO)

Observations of the disk-integrated solar Ca II K-line are made using the Evans Coronal Facility at The National Solar Observatory/ Sacramento Peak. A coelostat is used to feed the horizontal Littrow spectrograph and the spectrum from 3898-3954 angstroms is recorded by scanning the grating and digitizing the output of a photomultiplier. About 50-150 spectral scans are made each day. From 1976-1983 data was obtained on 10% of all days, while from 1984-present data is obtained on about 45% of all days. For more information see: http://www.sunspot.noao.edu/nsosp/data/cak_mon.html Data are also available from NOAA/NESDIS/NGDC Solar-Terrestrial Physics Program at: http://www.ngdc.noaa.gov/stp/stp.html