| 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.
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