[MIS17-P06] Observational Data in the first half of 20th century to join modern scientific Observation and historical documents: A Usage example ob Photographic Plate of Kwasan Observatory
Keywords:Sunspot, Geomagnetic Storm, Data Archive
In this report, as an example of utilizing such data, we will look at sunspot images and collation of images of chromosphere, CaK line heliograms by spectroheliography, and geomagnetism observation data in the first half of the 20th century .
Regarding the decades of the 1930s, when comparing photographic plate data of the solar CaK line heliogram photographed at Kwasan Observatory, Kyoto University, and the aa index which is one of the indicators of geomagnetic storms, it was found that geomagnetic storm of a scale exceeding -100 nT even when it occurred, it was recorded that none of sunspots, existed in nine cases. As an example, at the end of April 1933, sunspots were not seen in the Kwasan Observatory's CaK line heliogram and sunspot sketches in various places, but on May 1, a geomagnetic storm was observed in Kakioka, the aa index was about -200 nT. The advantage of the CaK line heliogram is that not only sunspots but also regions where relatively weak magnetic fields such as plague that is not visible with continuous light are distributed are visualized. This makes it possible to obtain information on the global magnetic neutral line where filaments causing coronal mass ejection can exist.