NDLI: Group Sunspot Numbers: A New Solar Activity Reconstruction ( Solar Physics , Volume 181 , Issue 2 )

Content Provider	Springer Nature Link
Author	Hoyt, Douglas V. Schatten, Kenneth H.
Copyright Year	1998
Abstract	In this paper, we construct a time series known as the Group Sunspot Number. The Group Sunspot Number is designed to be more internally self-consistent (i.e., less dependent upon seeing the tiniest spots) and less noisy than the Wolf Sunspot Number. It uses the number of sunspot groups observed, rather than groups and individual sunspots. Daily, monthly, and yearly means are derived from 1610 to the present. The Group Sunspot Numbers use 65941 observations from 117 observers active before 1874 that were not used by Wolf in constructing his time series. Hence, we have calculated daily values of solar activity on 111358 days for 1610–1995, compared to 66168 days for the Wolf Sunspot Numbers. The Group Sunspot Numbers also have estimates of their random and systematic errors tabulated. The generation and preliminary analysis of the Group Sunspot Numbers allow us to make several conclusions: (1) Solar activity before 1882 is lower than generally assumed and consequently solar activity in the last few decades is higher than it has been for several centuries. (2) There was a solar activity peak in 1801 and not 1805 so there is no long anomalous cycle of 17 years as reported in the Wolf Sunspot Numbers. The longest cycle now lasts no more than 15 years. (3) The Wolf Sunspot Numbers have many inhomogeneities in them arising from observer noise and this noise affects the daily, monthly, and yearly means. The Group Sunspot Numbers also have observer noise, but it is considerably less than the noise in the Wolf Sunspot Numbers. The Group Sunspot Number is designed to be similar to the Wolf Sunspot Number, but, even if both indices had perfect inputs, some differences are expected, primarily in the daily values.
Starting Page	491
Ending Page	491
Page Count	1
File Format	PDF
ISSN	00380938
Journal	Solar Physics
Volume Number	181
Issue Number	2
e-ISSN	1573093X
Language	English
Publisher	Kluwer Academic Publishers
Publisher Date	1998-01-01
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Astrophysics
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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Group Sunspot Numbers: A New Solar Activity Reconstruction ( Solar Physics , Volume 179 , Issue 1 )

Solar Physics : Volume 181, Issue 2, August 1998

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Group Sunspot Numbers: A New Solar Activity Reconstruction ( Solar Physics , Volume 181 , Issue 2 )

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