The Digital Database of Long-Term Solar Chromospheric Variation

From 1926 to 1969, a long term solar full disk observation was done by Kyoto University. Daily, Ca II K (393.4 nm) spectroheliographic images and white light images were recorded on photographic plates. In this report, we will give the current status of our project to digitize all these images and to construct a database of these images for public use through the IUGONET system. In addition, we will discuss our perspective on the scientific analysis of the database by taking the solar CaII K brightness as a proxy measure of the solar UV irradiance on the terrestrial upper atmosphere.