Solar White Light Faculae

Solar White Light Faculae are areas of bright plages on the solar disk. These were routinely measured at the Royal Greenwich Observatory in the UK from 1874 to 1976, producing a record of over 100 years of continuous monitoring of this solar phenomenon. Detailed positions and areas of sunspots and faculae for each day in the year are available. As part of a data rescue effort in 1999, NOAA had these analog records keyed into digital form.

The record includes photograph time, observing station (Greenwich, Cape of Good Hope, Kodaikanal, and Mauritius), group number, position of the spot group and/or faculae, area of the spots, and faculae area for each group. The dark sunspot group areas block the solar radiation from the Sun. The bright white light faculae enhance the solar radiation from the Sun. Models of the total solar irradiance include both these opposing forces of dark sunspot group areas and the bright white light faculae areas.

Greenwich data are also available via Solar Sunspot Regions in a different format, and compiled by Fred Ward, USAF AFCRL, in the 1960s and later updated by Doug Hoyt in the 1990s. The Greenwich data books have two sections and the data are somewhat different between the two sets.

  1. Greenwich White Light Faculae and Sunspot Area data by group 1874-1955 (Data documentation)
  2. Greenwich PhotoHeliographic Results -- Summary daily data (Data documentation) 1956-1976 -- daily projected umbral area and total sunspot area, daily projected faculae area for Eastern hemisphere, daily projected faculae area for the Western hemisphere, corrected umbral and total sunspot area, and corrected faculae areas for the Eastern and Western hemisphere.