J/A+A/652/A56 Hemispheric Sunspot Numbers 1874-2020 (Veronig+, 2021)
Hemispheric Sunspot Numbers 1874-2020.
Veronig A.M., Jain S., Podladchikova T., Poetzi W., Clette F.
<Astron. Astrophys. 652, A56 (2021)>
=2021A&A...652A..56V 2021A&A...652A..56V (SIMBAD/NED BibCode)
ADC_Keywords: Sun
Keywords: sun - sunspots - solar activity
Abstract:
Previous studies have shown significant North-South asymmetries for
various features and indicators of solar activity. These findings
suggest some decoupling between the two hemispheres over the solar
cycle evolution, supported by dynamo theories. For the most important
solar activity index, the sunspot numbers, so far only limited
coverage of hemispheric data is available.
The aim of this study is to create a continuous series of daily and
monthly hemispheric sunspot numbers (HSN) from 1874 until 2020, which
will be continuously expanded in the future with the HSN provided by
SILSO.
Based on the available daily measurements of hemispheric sunspot areas
from 1874-2016 from Greenwich Royal Observatory and NOAA, we derive
the relative fractions of the Northern and Southern activity. These
fractions are applied to the International Sunspot Numbers (ISN) to
derive the HSN. This method and obtained data are validated against
the HSN available for the period 1945-2004 from Temmer et al.
(2006A&A...447..735T 2006A&A...447..735T, J/A+A/447/735) and 1992 to date by SILSO.
Results: We provide a continuous data series and catalogue of daily,
monthly mean and 13-month smoothed monthly mean HSN for the time range
1874-2020, i.e. fully covering solar cycles no. 12 to 24, which are
consistent with the newly calibrated ISN (Clette et al.,
2014SSRv..186...35C 2014SSRv..186...35C). Validation of the reconstructed HSN against the
direct data available since 1945 reveals high consistency, with a
Pearson correlation coefficients of r=0.94 (0.97) for the daily
(monthly mean) data. The cumulative hemispheric asymmetries for cycles
12-24 give a mean value of 16%, with no obvious pattern in North-South
predominance over the cycle evolution. The strongest asymmetry occurs
for cycle no. 19, in which the Northern hemisphere shows a cumulated
predominance of 42%. The phase shift between the peaks of solar
activity in the two hemispheres may be up to 28 months, with a mean
absolute value over cycles 12-24 of 16.4 months. The phase shifts
reveal an overall asymmetry of the Northern hemisphere reaching its
cycle maximum earlier (in 10 out of 13 cases), with a mean signed
phase shift of -7.6 months. Relating the peak growth rates of the ISN
and HSN during the cycle's rise phase, respectively, with the cycle
amplitude reveals higher correlations when considering the two
hemispheres individually, with r=0.9.
Our findings provide further evidence that the evolution of the solar
cycle occurs partly independent for the two hemispheres, and
demonstrate that empirical solar cycle prediction methods can be
improved by investigating the solar cycle dynamics in terms of the
hemispheric sunspot number evolution.
Description:
We provide a catalogue that contains hemispheric sunspot numbers (HSN)
from 1874 until 2020. Catalogue A contains the daily data. Catalogue B
contains the monthly mean and 13-month smoothed monthly data. This
series will be continuously expanded in the future with the HSN
provided by the SILSO World Data Center (http://www.sidc.be/silso/).
The long-term HSN catalogue provided here was created using the
available daily measurements of hemispheric sunspot areas from
1874-2016 from Greenwich Royal Observatory and NOAA, from which we
derived the relative fractions of the Northern and Southern activity.
These fractions were subsequently applied to the International Sunspot
Numbers (ISN) to derive the HSN. This method and obtained data have
been validated against the HSN available for the period 1945-2004 from
Temmer et al. (2006A&A...447..735T 2006A&A...447..735T, Cat. J/A+A/447/735) and 1992-2020
by SILSO. The 13-month smoothed data presented in the catalogue uses
the optimized smoothing method described in Podladchikova et al.
(2017ApJ...850...81P 2017ApJ...850...81P).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catala.dat 58 53510 Daily Hemispheric Sunspot Numbers
(1874-05-01 to 2020-10-31)
catalb.dat 101 1758 Monthly Mean and 13-month smoothed Hemispheric
Sunspot Numbers (1874-05 to 2020-10)
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See also:
J/A+A/447/735 : Hemispheric Sunspot Numbers 1945-2004 (Temmer+, 2006)
Byte-by-byte Description of file: catala.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "YYYY/MM/DD" Date Date of calculated values
12- 16 F5.1 --- Dn Daily northern Sunspot Numbers combined
series (1874-05-01 to 2020-10-31)
18- 22 F5.1 --- Ds Daily southern Sunspot Numbers combined
series (1874-05-01 to 2020-10-31)
24- 28 F5.1 --- Dnarea Daily northern Sunspot Numbers
reconstructed from Sunspot Areas
(1874-05-01 to 2016-09-30)
30- 34 F5.1 --- Dsarea Daily southern Sunspot Numbers
reconstructed from Sunspot Areas
(1874-05-01 to 2016-09-30)
36- 40 F5.1 --- Dnt06 ?=-1 Daily northern Sunspot Numbers
recalibrated from Temmer et al., 2006,
Cat. J/A+A/447/735
(1945-01-01 to 2004-12-31)
42- 46 F5.1 --- Dst06 ?=-1 Daily southern Sunspot Numbers
recalibrated from Temmer et al., 2006,
Cat. J/A+A/447/735
(1945-01-01 to 2004-12-31)
48- 52 F5.1 --- Dnsil ?=-1 Daily northern Sunspot Numbers from
SILSO (1992-01-01 to 2020-10-31)
54- 58 F5.1 --- Dssil ?=-1 Daily southern Sunspot Numbers from
SILSO (1992-01-01 to 2020-10-31)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: catalb.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 "YYYY/MM" Date Date of calculated values
9- 13 F5.1 --- Mn Monthly northern Sunspot Numbers combined
series (1874-05 to 2020-10)
15- 19 F5.1 --- Ms Monthly southern Sunspot Numbers combined
series (1874-05 to 2020-10)
21- 25 F5.1 --- Mnsm ?=-1 Smoothed northern Sunspot Numbers combined
series (1874-05 to 2020-10)
27- 31 F5.1 --- Mssm ?=-1 Smoothed southern Sunspot Numbers combined
series (1874-05 to 2020-10)
33- 37 F5.1 --- Mnarea ?=-1 Monthly northern Sunspot Numbers
reconstructed from Sunspot Areas
(1874-05 to 2016-09)
39- 43 F5.1 --- Msarea ?=-1 Monthly southern Sunspot Numbers
reconstructed from Sunspot Areas
(1874-05 to 2016-09)
45- 49 F5.1 --- Mnareasm ?=-1 Smoothed northern Sunspot Numbers
reconstructed from Sunspot Areas
(1874-05 to 2016-09)
51- 55 F5.1 --- Msareasm ?=-1 Smoothed southern Sunspot Numbers
reconstructed from Sunspot Area
(1874-05 to 2016-09)
57- 61 F5.1 --- Mnt06 ?=-1 Monthly northern Sunspot Numbers
recalibrated from Temmer et al., 2006,
Cat. J/A+A/447/735(1945-01 to 2004-12)
63- 67 F5.1 --- Mst06 ?=-1 Monthly southern Sunspot Numbers
recalibrated from Temmer et al., 2006,
Cat. J/A+A/447/735(1945-01 to 2004-12)
69- 73 F5.1 --- Mnt06sm ?=-1 Smoothed northern Sunspot Numbers
recalibrated from Temmer et al., 2006,
Cat. J/A+A/447/735(1945-01 to 2004-12)
75- 79 F5.1 --- Mst06sm ?=-1 Smoothed southern Sunspot Numbers
recalibrated from Temmer et al., 2006,
Cat. J/A+A/447/735 (1945-01 to 2004-12)
81- 85 F5.1 --- Mnsil ?=-1 Monthly northern Sunspot Numbers from
SILSO (1992-01 to 2020-10)
87- 91 F5.1 --- Mssil ?=-1 Monthly southern Sunspot Numbers from
SILSO (1992-01 to 2020-10)
93- 96 F4.1 --- Mnsilsm ?=-1 Smoothed northern Sunspot Numbers from
SILSO (1992-01 to 2020-10)
98-101 F4.1 --- Mssilsm ?=-1 Smoothed southern Sunspot Numbers from
SILSO (1992-01 to 2020-10)
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Acknowledgements:
Astrid Veronig (Univ. Graz), astrid.veronig(at)uni-graz.at
Shantanu Jain (Skoltech), Shantanu.Jain(at)skoltech.ru
(End) A. Veronig 9Univ. Graz], S. Jain [Skoltech], P. Vannier [CDS] 16-Jun-2021