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Royal Observatory, Greenwich - USAF/NOAA Sunspot Data

(Funding for this database terminated in FY2005 and apparently will never be restored - We will continue to update if possible.) Last update 2014/06/12

Please note: Dr. David Hathaway, a member of the MSFC solar physics group for 29 years, has transferred (7/9/2014) to NASA's Ames Research Center in California. Dr. Hathaway will continue to update his solar cycle pages when he is settled. Dr. Hathaway's email address remains the same.

2012/08/02 - Yearly data files g2005.txt, g2006.txt, g2007.txt, and g2008.txt have been rewritten to correct a formatting error caught by Andrey Tlatov.

2012/04/02 - This database saw significant revisions. Over 120 days in which sunspots should have been observed do not have records and are now noted as missing days through the inclusion of records with year, month, and day but all other columns zeroed out in the raw data files (gYYYY.txt). The missing days are also enumerated in a file: MissingDays.txt. Accounting for these missing days, as well as the variation between 27 and 28 days in a Carrington Rotation, has also slightly changed the monthly sunspot area calculations and the values used in making the Butterfly diagram.

2012/04/02 - Another change is the deletion of data on sunspot umbral areas from 1977 to 1981. It is now clear that these numbers were fabricated using a model for the ratio of the umbral area to the whole spot area that has significant flaws. Also, Giuliana de Toma noted that the corrected and uncorrected whole spot areas were in disagreement starting in 1982. Starting in 1982 the corrected areas were the primary data and the uncorrected areas were calculated using the sunspot group distance from disk center. These values are now properly calculated.

Please note that, as before, the data in the raw data files (gYYYY.txt) are uncorrected for the change in data source in 1977. The derived data (daily_area.txt, sunspot_area.txt, sunspot_area_north.txt, sunspot_area_south.txt, and bflydata.txt) do include the correction factor of 1.4x after 1976/12/31.

Sunspots appear as dark spots on the surface of the Sun. They typically last for several days, although very large ones may live for several weeks. Sunspots are magnetic regions on the Sun with magnetic field strengths thousands of times stronger than the Earth's magnetic field. Sunspots usually come in groups with two sets of spots. One set will have positive or north magnetic field while the other set will have negative or south magnetic field. The field is strongest in the darker parts of the sunspots - the umbra. The field is weaker and more horizontal in the lighter part - the penumbra.

The Royal Greenwich Observatory (RGO) compiled sunspot observations from a small network of observatories to produce a dataset of daily observations starting in May of 1874. The observatory concluded this dataset in 1976 after the US Air Force (USAF) started compiling data from its own Solar Optical Observing Network (SOON). This work was continued with the help of the US National Oceanic and Atmospheric Administration (NOAA) with much of the same information being compiled through to the present. Unfortunately, the more recent data is given in a different format from the original and there are definite changes in the reported parameters from the different sources. In an effort to append the RGO data with the more recent data I have reformated the USAF and NOAA data to conform to the older RGO data format. The entire dataset is available below as ASCII text files containing records for individual years. Each file consists of records with information on individual sunspot groups for each day that spots were observed. The data format is given in a text file. The series of data files from 1874-2013 are also available in a single 5 Mb ZIP file.

Careful inspection of the data indicates that quantities such as sunspot area are not uniform across datasets or even within a given dataset. For example, the ratio of the umbral areas (the darker part of the sunspot) to total spot area (including the lighter penumbra) changes abruptly in 1941/1942 and the ratio of the total sunspot area to the sunspot number changes dramatically with the start of the USAF/NOAA data. In an effort to correct for these variations I have compared this data with the more uniform data compiled by Howard, Gilman, and Gilman (ApJ 283, 373, 1984) for the Mount Wilson photographic plate collection from 1917 to 1982. This comparison shows three epochs for the reported sunspot areas: for 1917-1941 Mt. Wilson Umbral Area = 0.35 RGO Umbral Area and Mt. Wilson Spot Area = 0.067 RGO Spot Area; for 1942-1968 Mt. Wilson Umbral Area = 0.41 RGO Umbral Area and Mt. Wilson Spot Area = 0.067 RGO Spot Area; for 1969-1981 Mt. Wilson Umbral Area = 0.59 RGO/USAF/NOAA Umbral Area and Mt. Wilson Spot Area = 0.094 RGO/USAF/NOAA Spot Area.

In producing my butterfly diagram (142 kb GIF image) (184 kb pdf-file) (showing total sunspot area as a function of time and latitude) I have retained the RGO Spot Areas prior to 1977 as reported but increased the USAF/NOAA Spot Areas by a factor of 1.4 after 1976. The data plotted in the Butterfly Diagram is contained in a 453KB ASCII text file with a single record containing the Carrington rotation number followed by five records containing 10 values each of the total sunspot area (in units of millionths of a hemisphere) found in 50 latitude bins distributed uniformly in Sine(latitude). Text files containing the monthly averages of the daily sunspot areas (again in units of millionths of a hemisphere) are also available for the full sun, the northern hemisphere, and the southern hemisphere. Another text file contains daily sunspot areas (1.51 Mb). These derived data include the correction factor of 1.4 for data after 1976. The missing days within the dataset are indicated by sunspot area values of -1 in the daily sunspot area file.

The yearly RGO and USAF/NOAA data files are:

folder g1874.txt 33kb text file
folder g1876.txt 20kb text file
folder g1878.txt 6kb text file
folder g1880.txt 59kb text file
folder g1882.txt 123kb text file
folder g1884.txt 154kb text file
folder g1886.txt 57kb text file
folder g1888.txt 20kb text file
folder g1890.txt 20kb text file
folder g1892.txt 176kb text file
folder g1894.txt 208kb text file
folder g1896.txt 90kb text file
folder g1898.txt 59kb text file
folder g1900.txt 21kb text file
folder g1902.txt 10kb text file
folder g1904.txt 104kb text file
folder g1906.txt 141kb text file
folder g1908.txt 128kb text file
folder g1910.txt 58kb text file
folder g1912.txt 12kb text file
folder g1914.txt 33kb text file
folder g1916.txt 174kb text file
folder g1918.txt 221kb text file
folder g1920.txt 106kb text file
folder g1922.txt 41kb text file
folder g1924.txt 45kb text file
folder g1926.txt 168kb text file
folder g1928.txt 199kb text file
folder g1930.txt 106kb text file
folder g1932.txt 36kb text file
folder g1934.txt 26kb text file
folder g1936.txt 206kb text file
folder g1938.txt 258kb text file
folder g1940.txt 161kb text file
folder g1942.txt 77kb text file
folder g1944.txt 28kb text file
folder g1946.txt 215kb text file
folder g1948.txt 295kb text file
folder g1950.txt 177kb text file
folder g1952.txt 73kb text file
folder g1954.txt 12kb text file
folder g1956.txt 290kb text file
folder g1958.txt 381kb text file
folder g1960.txt 247kb text file
folder g1962.txt 78kb text file
folder g1964.txt 29kb text file
folder g1966.txt 113kb text file
folder g1968.txt 225kb text file
folder g1970.txt 256kb text file
folder g1972.txt 171kb text file
folder g1974.txt 83kb text file
folder g1976.txt 32kb text file
folder g1978.txt 307kb text file
folder g1980.txt 301kb text file
folder g1982.txt 279kb text file
folder g1984.txt 112kb text file
folder g1986.txt 30kb text file
folder g1988.txt 220kb text file
folder g1990.txt 361kb text file
folder g1992.txt 232kb text file
folder g1994.txt 82kb text file
folder g1996.txt 23kb text file
folder g1998.txt 149kb text file
folder g2000.txt 266kb text file
folder g2002.txt 261kb text file
folder g2004.txt 94kb text file
folder g2006.txt 44kb text file
folder g2008.txt 9kb text file
folder g2010.txt 47kb text file
folder g2012.txt 137kb text file
folder g2014.txt 84kb text file
folder g1875.txt 30kb text file
folder g1877.txt 17kb text file
folder g1879.txt 9kb text file
folder g1881.txt 108kb text file
folder g1883.txt 136kb text file
folder g1885.txt 116kb text file
folder g1887.txt 34kb text file
folder g1889.txt 14kb text file
folder g1891.txt 95kb text file
folder g1893.txt 233kb text file
folder g1895.txt 162kb text file
folder g1897.txt 69kb text file
folder g1899.txt 29kb text file
folder g1901.txt 6kb text file
folder g1903.txt 58kb text file
folder g1905.txt 147kb text file
folder g1907.txt 148kb text file
folder g1909.txt 110kb text file
folder g1911.txt 21kb text file
folder g1913.txt 5kb text file
folder g1915.txt 141kb text file
folder g1917.txt 267kb text file
folder g1919.txt 171kb text file
folder g1921.txt 72kb text file
folder g1923.txt 18kb text file
folder g1925.txt 131kb text file
folder g1927.txt 180kb text file
folder g1929.txt 183kb text file
folder g1931.txt 59kb text file
folder g1933.txt 17kb text file
folder g1935.txt 98kb text file
folder g1937.txt 282kb text file
folder g1939.txt 220kb text file
folder g1941.txt 112kb text file
folder g1943.txt 38kb text file
folder g1945.txt 84kb text file
folder g1947.txt 326kb text file
folder g1949.txt 296kb text file
folder g1951.txt 141kb text file
folder g1953.txt 32kb text file
folder g1955.txt 89kb text file
folder g1957.txt 368kb text file
folder g1959.txt 343kb text file
folder g1961.txt 120kb text file
folder g1963.txt 62kb text file
folder g1965.txt 38kb text file
folder g1967.txt 257kb text file
folder g1969.txt 222kb text file
folder g1971.txt 169kb text file
folder g1973.txt 91kb text file
folder g1975.txt 35kb text file
folder g1977.txt 70kb text file
folder g1979.txt 413kb text file
folder g1981.txt 298kb text file
folder g1983.txt 179kb text file
folder g1985.txt 45kb text file
folder g1987.txt 71kb text file
folder g1989.txt 359kb text file
folder g1991.txt 357kb text file
folder g1993.txt 133kb text file
folder g1995.txt 48kb text file
folder g1997.txt 52kb text file
folder g1999.txt 204kb text file
folder g2001.txt 258kb text file
folder g2003.txt 160kb text file
folder g2005.txt 73kb text file
folder g2007.txt 23kb text file
folder g2009.txt 10kb text file
folder g2011.txt 133kb text file
folder g2013.txt 158kb text file

Sunspot Data Web Links

Solar Region Summary

Web Links
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NASA Logo Image Author: Dr. David H. Hathaway, david.hathaway @ nasa.gov
Curator: Mitzi Adams, mitzi.adams @ nasa.gov

Last Updated: July 09, 2014