J/A+A/602/A69 Group sunspot number series since 1739 (Chatzistergos+, 2017)
New reconstruction of the sunspot group numbers since 1739 using direct
calibration and 'backbone' methods.
Chatzistergos T., Usoskin I.G., Kovaltsov G.A., Krivova N.A., Solanki S.K
<Astron. Astrophys. 602, A69 (2017)>
=2017A&A...602A..69C 2017A&A...602A..69C (SIMBAD/NED BibCode)
ADC_Keywords: Sun
Keywords: Sun: activity - Sun: sunspots - methods: statistical
Abstract:
The group sunspot number (GSN) series constitute the longest
instrumental astronomical database providing information on solar
activity. This database is a compilation of observations by many
individual observers, and their inter-calibration has usually been
performed using linear rescaling. There are multiple published series
that show different long-term trends for solar activity.
We aim at producing a GSN series, with a non-linear non-parametric
calibration. The only underlying assumptions are that the differences
between the various series are due to different acuity thresholds of
the observers, and that the threshold of each observer remains
constant throughout the observing period.
We used a daisy chain process with backbone (BB) observers and
calibrated all overlapping observers to them. We performed the
calibration of each individual observer with a probability
distribution function (PDF) matrix constructed considering all daily
values for the overlapping period with the BB. The calibration of the
BBs was carried out in a similar manner. The final series was
constructed by merging different BB series. We modelled the
propagation of errors straightforwardly with Monte Carlo simulations.
A potential bias due to the selection of BBs was investigated and the
effect was shown to lie within the 1σ interval of the produced
series. The exact selection of the reference period was shown to have
a rather small effect on our calibration as well.
The final series extends back to 1739 and includes data from 314
observers. This series suggests moderate activity during the 18th and
19th century, which is significantly lower than the high level of
solar activity predicted by other recent reconstructions applying
linear regressions.
The new series provides a robust reconstruction, based on modern and
non-parametric methods, of sunspot group numbers since 1739, and it
confirms the existence of the modern grand maximum of solar activity
in the second half of the 20th century.
Description:
Annual, monthly, and daily values of the Group sunspot number series
produced in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
chgsny.dat 27 272 GSN series, annual values
chgsnm.dat 29 3264 GSN series, monthly values
chgsnd.dat 31 101184 GSN series, daily values
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See also:
VI/138 : Sunspots catalogues, 1853-1870 (Casas+, 2013)
J/A+A/390/707 : Hemispheric Sunspot Numbers 1975-2000 (Temmer+, 2002)
J/A+A/447/735 : Hemispheric Sunspot Numbers 1945-2004 (Temmer+, 2006)
J/A+A/584/A73 : Sunspot areas and tilt angles (Senthamizh Pavai+, 2015)
J/A+A/595/A104 : Scheiner drawing sunspot areas and tilt angles (Arlt+, 2016)
Byte-by-byte Description of file: chgsny.dat
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Bytes Format Units Label Explanations
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1- 6 F6.1 yr Date Observation date
8- 13 F6.2 --- Rg ?=-99 Group sunspot number
15- 20 F6.2 --- sigmaU ?=-99 Upper limit of standard deviation
22- 27 F6.2 --- sigmaL ?=-99 Lower limit of standard deviation
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Byte-by-byte Description of file: chgsnm.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.year Year of observation
6- 7 I2 --- Obs.month Month of observation
10- 15 F6.2 --- Rg ?=-99 Group sunspot number
17- 22 F6.2 --- sigmaU ?=-99 Upper limit of standard deviation
24- 29 F6.2 --- sigmaL ?=-99 Lower limit of standard deviation
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Byte-by-byte Description of file: chgsnd.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.year Year of observation
6- 7 I2 --- Obs.month Month of observation
9- 10 I2 d Obs.day Day of observation
12- 17 F6.2 --- Rg ?=-99 Group sunspot number
19- 24 F6.2 --- sigmaU ?=-99 Upper limit of standard deviation
26- 31 F6.2 --- sigmaL ?=-99 Lower limit of standard deviation
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Acknowledgements:
Theodosios Chatzistergos, chatzistergos(at)mps.mpg.de
(End) Theodosios Chatzistergos [MPS], Patricia Vannier [CDS] 27-Feb-2017