Solar Calcium Plages

Solar observatories monitor the Sun in the calcium (Ca) K line wavelength by using a filter that allows only this wavelength's light through, calcium filtergrams, or spectroheliograms. Daily full disk calcium K232 images are reduced to provide calcium plage positions and areas or summed to produce a daily Ca K index. Ca K active regions can be seen moving across the solar disk, above the white light sunspot regions, and higher in the solar atmosphere (chromosphere).


Calcium Data

  • Daily Calcium Plage Areas from Mt. Wilson Observatory 1915-1984 -- Peter Foukal
  • San Fernando Observatory K-line facular data -- Gary Chapman
    1988-1998 -- daily areas and irradiance indices, such as the excess spectral irradiance in the K line 393.4 nm (ASCII)
  • Daily calcium plage reduced data, including position, areas and intensities

  • Hale Observatory (Mt. Wilson Solar Observatory -- Oct 1979-Sep 1981):
    Data Documentation
  • Mt. Wilson Solar Observatory:
    Data Documentation
  • McMath Solar Observatory:
    Data Documentation
  • Big Bear Solar Observatory:
    Data Documentation

Calcium K index

Daily summary data -- includes YYMMDD, number of plage regions, total corrected plage area, and Calcium plage index

  • Big Bear Solar Observatory:
    Data Documentation
  • McMath Solar Observatory:
    Data Documentation
  • Sacramento Peak Solar Observatory:
    Data Documentation

SGD Tables

  • Solar-Geophysical Data Regions of Solar Activity Table 1969-1982 (Documentation)
  • Daily white light sunspot regions are tied to the overlying Ca K plage regions each day.