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Solar Chromosphere Data in Calcium Wavelength
Observing the Sun in the Calcium wavelengths provides scientists with information about the processes occurring at different altitudes in the solar atmosphere. For many years, 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, producing calcium filtergrams or spectroheliograms. In the Ca K wavelength one sees bright areas or "plages" (a French word meaning beaches), occurring above sunspot regions. They are located in the chromosphere, at a higher altitude in the solar atmosphere than the sunspot regions in the photosphere. These hot plages or active regions move across the Sun and grow and decay along with the sunspot regions. Daily full disk Calcium K images are reduced to provide Calcium plage positions, areas and intensities or a daily index of the total area. NGDC archives solar Calcium images, reduced tabular data and daily indices.