Validation/Reconstruction of the Sunspot Number Record, 1841-2007
[ ] L. Svalgaard Easy Tool Kit, Inc., Houston, TX
IUGG July 2007
Sunspot Number (SSN) Applications
- Solar Dynamo- Space Weather/Climate- Cosmic Ray Modulation- Climate Change
Two SSN Series
RINT: 1700 - 2007 (SIDC/ROB)
RG : 1610 - 1995 (Hoyt & Schatten, 1998)
020406080
100120140160180200
1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Rz
Rg
Sunspot Number Series
1918171615141312111098 20 21 22 23
SSN
Dec
HF
Ellis (1898)
SSN correlated with daily range of geomagnetic elements
SR Ionospheric Current System (Torta et al., 1997)
SR at Hobarton (1848)
Wolf (1875) used the SSN-daily range relationship to adjust the SSN for years before 1848
Rudolf Wolf
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
1740 1750 1760 1770 1780 1790 1800 1810 1820 1830 1840 1850 1860 1870 1880
Evolution of Wolf Sunspot Numbers
W1861 / Rnow
W1875 / Rnow W1880 / Rnow
W1857 / Rnow
Staudacher
2x
25%
y = 0.9301x1.0391
R2 = 0.8932
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70
HON
1902-2003rY NGK
rY HON
Step 1
Show that over extended periods of time (decades, centuries) constant, stablerelationships exist between rY at stations such as Niemegk and Honolulu that arewidely separated in longitude and latitude.
0
10
20
30
40
50
60
70
1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
rY (nT)
Median of SR normalized to NGK
Step 2
0
10
20
30
40
50
60
70
1840 1850 1860 1870 1880 1890 1900 1910 1920 1930
Backbone
OSL
rY (nT)
Link together observations of the regular variation observed at long-term stations (normalizing to Niemegk and using Oslo to bridge the gaps for early years) to obtain the variation of SR since 1840
Step 3
Relate average rY to RINT ( & F10.7)
The daily range rY is highly correlated with RINT & F10.7 at all phases of the sunspot cycle
Step 3 (continued)
Use the RINT vs. rY relationship to obtain a new SSN series back to 1840
Step 4
Step 5Cycle Rg Rz
9 1.347 1.02010 1.545 1.31711 1.572 1.19112 1.580 1.37913 1.343 1.40314 1.121 1.15615 1.075 1.18016 1.103 1.23817 1.093 1.16618 1.046 0.99619 0.991 0.90520 0.978 0.97021 0.986 0.98222 0.961 0.94823 1.026 1.036
Correction Factors forreported sunspot numbers.
Obtain correction factors for each cycle for the International and Group SSN series
Provisional SSN Series:Cycles 10 & 11 comparable to 22 & 23
Work in Progress
- Strengthen 1840-present series- Extend before 1840- Determine causes of jumps in 1893 & 1945 - Determine effect of Earth’s decreasing dipole (~10% since 1840)