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Sunspot Number Data
The sunspot number (SN) is a widely used indicator of solar activity.
The relative number of sunspots - the daily index of solar activity - was introduced in 1848 by
the Swiss
astronomer Rudolf Wolf and named the Wolf number.
From 1849 to 1980, Wolf numbers were regularly determined at the Zurich Observatory in Switzerland (a reliable series).
There are also series of Wolf numbers, restored according to indirect data for the era preceding 1849:
the average monthly sunspot number since 1749 (restored, numbered series) and
the average annual
number since 1700. Modern researchers have managed
to qualitatively extend this series by single telescopic
observations to 1611.
Currently, a summary of all observations of sunspots and the determination of the monthly and annual averages
of the International Sunspot Number is carried out at the Solar Influences Data Analysis Center (SIDC)
of the Royal Observatory of Belgium in Brussels.
The time series of the sunspot number are published on the website of the World Data Center for the production,
preservation and dissemination of the international sunspot number -
WDC-SILSO.
Since July 1, 2015, the SN index is available in WDC-SILSO in two forms:
sunspot number, introduced by R. Wolf in 1849 (version 1.0),
and group number - a new completely redesigned data series
(version 2.0).
The International sunspot number
The calculation of the sunspot number has been conducted by the National Oceanic and Atmospheric Administration of the United States
- NOAA, US since 1944.
The sunspot number determined by NOAA is called The American relative sunspot number - NOAA sunspot number
The data is published on the website of the National Centers for Environmental Information NOAA -
NCEI NOAA
based on the "Solar Bulletin" of the American Association of Variable
Star Observers - AAVSO.
The American relative sunspot number
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