University of Oulu

Takalo, J. Temporal and Latitudinal Variation in Penumbra-Umbra Ratios of the Sunspots: Analyses of RGO, Kodaikanal and Debrecen Databases. Sol Phys 298, 63 (2023).

Temporal and latitudinal variation in penumbra-umbra ratios of the sunspots : analyses of RGO, Kodaikanal and Debrecen databases

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Author: Takalo, Jouni1
Organizations: 1Space Physics and Astronomy Research Unit, University of Oulu, POB 3000, FIN-90014, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.6 MB)
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Language: English
Published: Springer Nature, 2023
Publish Date: 2023-09-05


We study the latitudinal distribution and temporal evolution of the sunspot penumbra-umbra ratio (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-values 5.20 (4.75), Kodaikanal even (odd) cycles have q-values 5.27 (5.43), and Debrecen cycles have q-value 5.74 on the average.

We also show that 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-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-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-graphs, although GG exists in their temporal total area and umbral area.

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Series: Solar physics
ISSN: 0038-0938
ISSN-E: 1573-093X
ISSN-L: 0038-0938
Volume: 298
Issue: 5
Article number: 63
DOI: 10.1007/s11207-023-02161-2
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Dataset Reference: The RGO sunspot area data are from RGO-USAF/ NOAA (, Kodaikanal database from and Debrecen sunspot datasets from The dates of the cycle maxima were obtained from the National Geophysical Data Center (NGDC), Boulder, Colorado, USA (, and the corona indices are retrieved from
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