Plage and Enhanced Network Indices Derived from Ca II K Spectroheliograms

Abstract

NSO Sacramento Peak Ca II K images are analyzed for the years 1992 through September 1996 with about a 50% coverage,. The plage, decayed plage, enhanced network, and quiet-Sun features are identified on each image with an algorithm that uses the criteria of intensity, size, and filling factor. These algorithms can be adapted for analyzing spectroheliograms from ground-based or space-based observatories. Plage and enhanced network indices, for these time periods, are shown. We present intensity contrasts for the plage, decayed plage, and enhanced network. We also find that these contrasts, which are an average of the structures intensity relative to the quiet Sun over the whole disk, remain essentially constant over the solar cycle.

Paper presented at the SOLERS22 International Workshop, held at the National Solar Observatory, Sacramento Peak, Sunspot, New Mexico, U.S.A., June 17–21, 1996.