Temporal and Latitudinal Variation in Penumbra-Umbra Ratios of the Sunspots: Analyses of RGO, Kodaikanal and Debrecen Databases

Abstract

AbstractWe study the latitudinal distribution and temporal evolution of the sunspot penumbra-umbra ratio ($q$ q ) for the even and odd Solar Cycles 12 – 24 of RGO sunspot groups, SC21 – SC24 of Debrecen sunspot groups and Kodaikanal sunspot dataset for SC16 – SC24. We find that RGO even (odd) Cycles have $q$ q -values 5.20 (4.75), Kodaikanal even (odd) cycles have $q$ q -values 5.27 (5.43), and Debrecen cycles have $q$ q -value 5.74 on the average.We also show that $q$ q is at its lowest around the Equator of the Sun and increases towards higher latitudes having maximum values at about 10 – 25 degrees. This is understandable because smaller sunspots and groups locate nearer to the Equator and have smaller $q$ q -values than larger sunspots and groups, which maximize at about 10 – 20 degrees at both hemispheres. The error limits are very wide, and, thus, the confidence in this result is somewhat vague.For the Debrecen dataset, we find a deep valley in the temporal $q$ q -values before the middle of the cycle. We show that this exists simultaneously with the Gnevyshev gap (GG) in the graph of the total and umbral areas of the large sunspot groups. Other databases do not show GG in their $q$ q -graphs, although GG exists in their temporal total area and umbral area.