Carrington maps of Ca II K-line emission for the years 1915-1985

Abstract

We have used Mount Wilson Observatory calcium K-line images, digitized and flat fielded by the solar group at UCLA, to construct Carrington maps of CaII 3934 intensity for the years 1915-1985. These maps have a spatial resolution comparable to the resolution of Carrington maps of the magnetic field observed at Kitt Peak and a spectral resolution comparable to the width of the K 232 emission. Consequently, they provide a way of tracking the spatial distribution of magnetic flux from the present back to the year 1915. In this paper, we compare some of the recent K-line maps with corresponding maps of magnetic field, and show examples of K-line maps during earlier sunspot cycles when high-quality magnetograms were not available. Then, we use butterfly diagrams and super-synoptic displays to summarize the long-term evolution of the patterns of calcium intensity. Although each cycle has characteristics that are similar to the others, cycle 19 is remarkable for its broad latitudinal distribution of active regions, for its giant poleward surges of flux, and for the emergence of a north-south asymmetry that lasted 10 years.