Evolutionary Charts of Solar Activity (Calcium Plages) as Functions of Heliographic Longitude and Time 1964-1979

The richness and diversity of data relating to solar activity present a challenge from the point of view of organization and evaluation. For phenomena such as plages and centers of activity that tend to last for more than one solar rotation, we have prepared a sequence of evolutionary charts based on heliographic longitude for successive solar rotations. Such a diagrammatic representation of calcium plages as a function of longitude and time, coupled with considerations of heliographic latitude, permits relatively easy and confident recognition of successively returning centers of activity. In past years, certain studies of solar activity prepared at the former McMath-Hulbert Observatory of the University of Michigan have used the format of such evolutionary charts to organize the chromospheric aspects of long enduring solar activity for time intervals of several years. These charts have proved useful in recognizing patterns of large scale organization on the sun. It is possible that solar activity organized in this manner for 16 years, somewhat more than an entire solar cycle, can provide guidance for the interpretation of other aspects of solar activity and of phenomena of the interplanetary medium including sector boundaries, geomagnetic activity, energetic particle events and solar wind streams. To this end, evolutionary charts have been prepared on the basis of McMath-Hulbert Observatory data and diagrams. These charts organize data relating to practically all calcium plages reported by the McMath-Hulbert Observatory to World Data Center A for Solar-Terrestrial Physics Boulder in the years 1964-1979.