Solar Calcium Plage Data

Data (All ftp)

Solar observatories have monitored 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).

Daily Calcium Plage Areas and Network Areas from Mt. Wilson Observatory Apn Data 1915-1999 -- Peter Foukal

  • The Apn data include both the Active Region (AR) calcium plage areas, as in the Ap, and also the areas of the active network. The Apn is NOT corrected for foreshortening (useful for irradiance models) and so is expressed in fractions of the solar disk. The basic reduction procedure is given in GRL 25, 2909 (1998), but the values were revised somewhat in a later paper in GRL 29, 2089 (2002). The annual means of these data agree very well with the independent time series of the Mt. Wilson areas by Ulrich et al., and by Tlatov et al. -- see P. Foukal, Solar Physics 255, 229 (2009). The data are plain text files of monthly mean and annual mean values of (plage + active network) areas, covering the period 8/1915 - 12/1999 inclusive, and expressed as fractions of the solar disc (i.e. not corrected for foreshortening). Data prior through 1984 are means of daily Mt. Wilson measurements; data after 1984 are based on four roughly evenly spaced days per month using Sacramento Peak observations.
  • Monthly Calcium Plage and Network Areas (in fractions of solar disk) in data and plot (pdf) form
  • Smoothed Monthly Calcium Plage and Network Areas (in fractions of solar disk) in data and plot (pdf) form
  • Plot of both the smoothed and unsmoothed Apn with International Sunspot Number -- Calcium Plage and Network Areas (in fractions of solar disk) plot

The following Ap daily data (no network included) are corrected for foreshortening, and so are expressed in fraction of a hemisphere. It is important to stress that these are just areas of the Active Region (AR) plages -- just like the McMath Plage Index (except the McMath Index incorporates estimates of brightness, whereas Ap is just area). The reference for these data is the GRL 23, 2169 (1996) paper by P. Foukal. Both the McMath index and the Ap are of limited use now that the Apn (area of plage plus active network) is available.

San Fernando Observatory K-line facular data -- Gary Chapman

Daily calcium plage reduced data, including position, areas and intensities

Solar observatories contributing to this database include McMath Solar Observatory (1942-Sep 1979), Hale Observatory (Mt. Wilson Solar Observatory -- Oct 1979-Sep 1981), and Big Bear Solar Observatory (Oct 1981-Oct 1987)

Daily summary data of the McMath/Hale/BigBear database 1942-1987

Includes YYMMDD, number of plage regions, total corrected plage area, and Calcium plage index for that day.

Big Bear Solar Observatory Calcium K Index

Sacramento Peak Solar Observatory Daily Calcium K Index

SGD Table

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