Solar Activity – Past, Present,
and Futuremmm
Leif Svalgaard
HEPL, Stanford University
TIEMS Conference, Oslo, Oct. 22, 2012
1
Indicators of Solar Activity
• Sunspot Number (and Area,
Magnetic Flux)
• Solar Radiation (TSI, UV, …,
F10.7)
• Cosmic Ray Modulation
• Solar Wind
• Geomagnetic Variations
• Aurorae
• Ionospheric Parameters
• Oscillations
• Climate?
• More…
Longest direct
observations
Penumbra
Umbra
After Eddy, 1976
Solar Activity is Magnetic Activity
2
The Sunspot Number(s)
• Wolf Number = KW (10*G + S)
• G = number of groups
• S = number of spots
• Group Number = 12 KG G
Douglas Hoyt and Kenneth
Schatten devised the Group
Sunspot Number using just
the group count (1993).
Unfortunately a K-factor
was also necessary here,
so the result really depends
on how well the K-factor
can be determined
Rudolf Wolf (1816-1893)
Observed 1849-1893
Ken Schatten
3
The Wolf Number, Zürich Sunspot Number, and International Sunspot
Number are all synonyms for the same data, today maintained by the
Solar Influences Data Center, SIDC, in Brussels, Belgium
Problem with The ‘Wolf’ Number
The effect of Weighting the sunspot count…
Zürich Observers
Wolf
Wolfer
Brunner
Waldmeier
1849-1893
1876-1928
1929-1944
1945-1995
4
Waldmeier’s Description of the Weighting
of Sunspots that began in the 1940s
Zürich
Locarno
1968
“A spot like a fine point is counted as one spot; a larger spot, but still without
penumbra, gets the statistical weight 2, a smallish spot with penumbra gets 3,
and a larger one gets 5.” Presumably there would be spots with weight 4, too.
This very important piece of metadata was strongly downplayed and is not generally known
5
Locarno, a week later
No Weight
2
4
4
6
2
4
2
2
1
2
1
SDO AIA 450nm
SDO HMI LOS
Combined Effect
of Weighting and
More Groups is
an Inflation of the
Relative Sunspot
Number by 20+%
I have re-counted
43,000 spots without
weighting for the last
ten years of Locarno
observations.
30
Groups
‘Spots’
10*11+52=162; 10*11+30=140;
162/140=1.16
6
Double-Blind Test of My Re-Count
I proposed to the Locarno
observers that they should
also supply a raw count
without weighting
Marco Cagnotti
For typical number of spots
the weighting increases the
‘count’ of the spots by 3050% (44% on average)
7
Comparison Zurich Sunspot Number and That Derived from Sunspot Areas
300
1000
Monthly Means
Rz
Rz
Rz
250
100
Rc = 0.3244*SA0.732
10
200
1
0.1
1
10
100
1000
10000
SA
SA
0.1
150
100
50
0
1875
1880
1885
1890
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
Comparison Zurich Sunspot Number and That Derived from Sunspot Areas
300
0.732
RZ /SA
>1000 uH
Monthly Means
0.7
Rz
250
(projected)
0.8
Monthly Means
0.6
0.5
0.732
Rc = 0.3244*SA
0.4
0.3
0.2
200
0.1
Wolfer
Brunner
Waldmeier
SIDC
0
1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
150
100
50
0
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
The 20% Inflation Caused by Weighting Spot Counts
2000
8
Correcting for the 20% Inflation
Sunspot Number (Official SIDC View)
200
180
Rcorr = Rofficial * 1.2 before ~1946
160
140
120
100
80
60
40
20
0
1700
1725
1750
1775
1800
1825
1850
1875
1900
1925
1950
1975
2000
This issue is so important that the
official agencies responsible for
producing sunspot number series
have instituted a series of now
ongoing Workshops to, if at all
possible, converge to an agreed
upon, common, corrected series:
http://ssnworkshop.wikia.com/wiki/Home
The inflation due to weighting is now
an established and accepted fact
Modern Grand Max?
GSN
That the corrected sunspot number is so
very different from the Group Sunspot
Number is a problem for assessing past
solar activity and for predicting future
activity. This problem must be resolved.
9
Problem with the
Group Sunspot Number
Determining correct K-factors…
10
The Ratio between the Group Sunspot
Number and the [corrected] Sunspot number
Shows that the significant discrepancy is largely due to data from the 1880s
11
Wolf-Wolfer Groups
Number of Groups: Wolfer vs. Wolf
9
Wolfer
8
Yearly Means 1876-1893
7
6
Wolfer = 1.653±0.047 Wolf
5
R2 = 0.9868
Wolfer
4
3
2
80mm 64X
1
Wolf
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Number of Groups
12
10
Wolf*1.653
8
Wolfer
Wolf
6
4
Wolf
37mm 20X
2
0
1865
1870
1875
1880
1885
1890
1895
12
Why are these so different?
Observer
This is the main reason
for the discrepancy
K-Factors
H&S RGO to Wolfer
Begin
K-factors
End
1.8
Wolfer, A., Zurich
2% diff.
Wolf, R., Zurich
Schmidt, Athens
Weber, Peckeloh
Spoerer, G., Anclam
Tacchini, Rome
Moncalieri
Leppig, Leibzig
Bernaerts, G. L., England
Dawson, W. M., Spiceland, Ind.
Ricco, Palermo
Winkler, Jena
Merino, Madrid
Konkoly, Ogylla
Quimby, Philadelphia
Catania
Broger, M, Zurich
Woinoff, Moscow
Guillaume, Lyon
Mt Holyoke College
1.094
1.117
1.135
0.978
1.094
1.059
1.227
1.111
1.027
1.01
0.896
1.148
0.997
1.604
1.44
1.248
1.21
1.39
1.251
1.603
1
1.6532
1.3129
1.5103
1.4163
1.1756
1.5113
1.2644
0.9115
1.1405
0.9541
1.3112
0.9883
1.5608
1.2844
1.1132
1.0163
1.123
1.042
1.2952
1876
1876
1876
1876
1876
1876
1876
1876
1876
1879
1880
1882
1883
1885
1889
1893
1897
1898
1902
1907
1928
1893
1883
1883
1893
1900
1893
1881
1878
1890
1892
1910
1896
1905
1921
1918
1928
1919
1925
1925
This
analysis
1.6
1.4
1.2
1
H&S
0.8
0.8
1
1.2
1.4
1.6
1.8
2
Zürich Classification:
a
b
½ of all
groups
Wolf couldn’t see most a & b
groups with his small telescope
A still unresolved question is how Hoyt & Schatten got the K-factors so wrong
13
Comparing G.
Spörer & Rev.
A. Quimby
[Philadelphia]
to Wolfer
Number of Groups
14
12
Spörer*1.416
10
8
6
Wolfer
4
Spörer
2
0
1860
Same good and stable fit,
showing that Wolfer’s count
had not drifted with time
12
1865
1870
1875
1880
1885
1890
1895
1900
1905
10
Tacchini * 1.176
8
Number of Groups
9
6
Wolfer
4
8
Tacchini
Quimby*1.284
2
7
0
1865
6
1870
1875
1880
1885
1890
1895
1900
1905
1910
Wolfer
9
5
8
7
4
6
Wolfer
Moncalieri * 1.511
5
3
4
Quimby
2
3
Moncalieri
2
1
0
1885
1
0
1870
1890
1895
1900
1905
1910
1915
1920
1925
1875
1880
1885
1890
1895
14
1900
Constructing a Composite
Comparing 22 observers that overlap with each other one can construct a
composite group number successively back to Schwabe and up to Brunner:
Comparison Composite Groups and Scaled Zurich SSN
14
Composite
Zurich
12
10
8
6
4
2
0
1820
1830
1840
1850
1860
1870
1880
1890
1900
1910
1920
1930
1940
There is now no systematic difference between the Zürich SSN and a Group
SSN reconstructed here by using correct K-factors relative to Wolfer.
15
Geomagnetic Calibration of
Sunspot Numbers
Wolf did it…
16
Geomagnetic Regimes
1) Solar UV maintains the ionosphere and influences the daytime field.
2) Solar Wind creates the magnetospheric tail and influences mainly the
nighttime field
17
Wolf’s Discovery: rD = a + b RW
.
North X
rY
Morning
H
rD
Evening
D
East Y
Y = H sin(D)
dY = H cos(D) dD
For small D, dD and dH
A current system in the ionosphere [E-layer] is
created and maintained by solar FUV radiation.
Its magnetic effect is measured on the ground.
(George Graham, 1722)
18
The Diurnal Variation of the Declination for
Low, Medium, and High Solar Activity
8
6
9
10
Diurnal Variation of Declination at Praha (Pruhonice)
dD'
4
1957-1959
1964-1965
2
0
-2
-4
-6
-8
-10
Jan
Feb
Mar
Apr
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Year
Diurnal Variation of Declination at Praha
8
6
May
dD'
1840-1849
rD
4
2
0
-2
-4
-6
-8
-10
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Year
19
Wolf got Declination Ranges for Milan from Schiaparelli
and it became clear that the pre-1849 SSNs were too low
Justification for Adjustment to 1861
1874 List
160
R Wolf
140
'1874 List' 1836-1873
120
Wolf = 1.23 Schwabe
100
'1861 List' 1849-1860
Wolf
80
60
'1861 List' 1836-1848
Schwabe
40
20
rD' Milan
0
4
5
6
7
8
9
10
11
12
13
The values for 1836-1848 came from Schwabe.
Wolf decided to increase them by 25% to match
his own relationship with Milan’s Declination
The smallest non-zero SSN
should be 11. When it is not,
it indicates adjustments were
made
The ‘1874’ list included the 25% [Wolf said 1/4] increase of the pre-1849 SSN.
Was this a sensible thing to do?
20
Wolf’s Original Geomagnetic Data
Wolf and Wolfer's Diurnal Ranges of Declination for their Long-running Stations
14
dD'
12
10
8
6
4
Praha (Prague) - Christiania (Oslo) - Milano (Milan) - Wien (Vienna)
2
0
1835
1840
1845
1850
1855
1860
1865
1870
1875
1880
1885
1890
1895
1900
1905
1910
1915
1920
1925
Diurnal Range Compared to Scaled International Sunspot Number
70
RI*
60
rY (nT)
50
40
30
20
10
Today we know that the relevant parameter is the East Component, Y, rather
than the Declination, D. Converting D to Y restores the stable correlation,
especially around the critical time near 1885 where the GSN begins to deviate
0
1835
1840
1845
1850
1855
1860
1865
1870
1875
1880
1885
1890
1895
1900
1905
1910
1915
1920
1925
Wolf found a
very strong
correlation
between his
Wolf number
and the daily
range of the
Declination.
Wolfer found
the original
correlation
was not
stable, but
was drifting
with time and
gave up on it
in 1923.
21
Using rY from nine
station ‘chains’ we
find that the
300
F10.7
250
y = 5.4187x - 129.93
R2 = 0.9815
200
correlation
150
Canonical Relationship SSN and F10.7
250
1952-1990
F10.7
200
100
y = 0.043085x 2.060402
R2 = 0.975948
150
100
50
y = -0.0000114x 3 + 0.0038145x 2 + 0.5439367x + 63.6304010
R2 = 0.9931340
50
SSN
rY
0
0
20
40
60
80
100
120
140
160
180
200
0
30
35
40
45
50
55
60
nT 70
65
between F10.7 and
rY is extremely
good (more than
98% of the
variation is
accounted for)
Solar Activity From Diurnal Variation of Geomagnetic East Component
250
200
Nine Station Chains
F10.7 sfu
F10.7 calc = 5.42 rY - 130
150
100
12
13
14
15
16
17
18
19
20
21
22
23
1980
1990
2000
50
25+Residuals
0
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
2010
This establishes that Wolf’s procedure and calibration are physically sound,
and that the diurnal variation gives us a method for calibration of the SSN
2020
22
Solar Wind in the Past
The Geomagnetic Record Allows
us to Reconstruct the Solar Wind
Properties for the Past 180 years
23
24-hour running means of the Horizontal Component of the low- & midlatitude geomagnetic field remove most of local time effects and leaves a
Global imprint of the Ring Current [Van Allen Belts]:
A quantitative measure of the effect can be formed as a series of the unsigned
differences between consecutive days: The InterDiurnal Variability, IDV-index.
24
Similar to Bartels’ u-index and the ‘Nachstörung’ popular a century ago.
IDV is strongly correlated with solar wind
magnetic field B, but is blind to solar wind speed V
nT
10
10
So, from IDV we can
get HMF B
B obs
8
8
B calc from IDV
6
6
B obs median
4
4
B std.dev
2
2
100% =>
18
Coverage
0
0
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
16
IDV vs. Solar Wind Speed V (1963-2010)
IDV
14
HMF B as a Function of IDV09
10
B nT
12
1963-2010
10
8
8
6
6
4
2
4
y = 1.4771x0.6444
2
R = 0.8898
y = 0.4077x + 2.3957
2
R = 0.8637
4
10
0
0
2
6
8
12
14
2
R = 0.0918
2
V km/s
IDV
16
0
350
400
450
500
550
25
The IHV Index gives us BV2
Calculating the variation
(sum of unsigned differences
from one hour to the next) of
the field during the night
hours [red boxes] from
simple hourly means (the
Interhourly Variation) gives
us a quantity that correlates
with BV2 in the solar wind
26
Physical meaning of IHV: the index is directly proportional to
the auroral power input, HP, to the polar regions
POES
27
Polar Cap Diurnal Variation gives us V times B
E=-VxB
This variation has
been known for more
than 125 years
28
Overdetermined
System: 3 Eqs,
2 Unknowns
B
= p (IDV)
BV2 = q (IHV)
Gjøa
VB = r (PCap)
Here is B back to the 1830s:
Heliospheric Magnetic Field at Earth
10
9
B
8
7
6
5
4
3
HMF from IDV-index
2
HMF observed in Space
1
0
1830
1840
1860
1870
1880
1890
1900
1910
1920
1930
1940
Cosmic Ray Modulation Parameter
1400
ϕ
1200
1850
1950
1960
1970
1980
1990
2000
2010
29
The Cosmic Ray Record has
Promise, but is not without Problems
17 pounds/yr
2 oz/year
Steinhilber et al. 2012
30
Cosmic Ray Modulation as Governed by
Strength of Magnetic Field in Heliosphere
Heliospheric Magnetic Field at Earth
10
B
9
8
7
6
5
4
3
HMF Observed in Space
HMF deduced from Geomagnetic Record
2
1
0
1830
1840
1850
1860
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
Cosmic Ray Modulation Parameter
1400
ϕ
Problem
1200
Observed Modulation
1000
800
600
400
200
0
1830
HMF scaled to Neutron Monitor Modulation
1840
1850
1860
1870
1880
1890
1900
1910
1920
1930
Ion
1940
Neutron
1950
1960
1970
1980
1990
2000
201031
31
Total Solar Irradiance at 1 AU
Predictions of SC24
Prediction of Solar Cycles
North - South Solar Polar fields [microTesla]
We are here now
State of the Art
From NOAA-NASA Panel
400
WSO
MSO*
300
200
100
0
1965
-100
1970
1975
1980
1985
1990
1995
2000
2005
2010
2015
-200
Polar Field Reversal
at Solar Maximum
-300
-400
Solar Dipole Divided by Sunspot Number for Following Maximum
4.0
3.5
3.0
Polar Field Precursor Method
WSO
R24
2.5
45
2.0
1.5
20
21
22
23
24
72
1.0
Min
0.5
0.0
1965
1970
1975
1980
1985
1990
1995
165
2000
2005
2010
2015
32
How is Cycle 24 Evolving? As Predicted!
2016
5002016
4502016
4002016
3502016
3002016
2016
250
2017
200
2017
150
2017
100
2017
50 21
2017
0
2017
1980
2017
2017
6
7
8
9
10
11
12
1
2
3
4
5
6
19857
8
2016.458
Active Region Count
2016.542
2016.625 Numbered Active Regions per Month
2016.708
2016.792
2016.875
Prediction
2016.958
2017.042
2017.125
2017.208
2017.292
22
23
24
2017.375
2017.458
1990
1995
2000
2005
2010
2015
2020
2017.542
2017.625
D. Hathaway
300
250
200
150
100
22
14
21
50
0
1983
24
1984
1985
1986
1987
1988
1989
1990
SIDC
33
Observed Sunspot Number Divided by Synthetic SSN (1952-1990)
1.4
600
SIDC
1.2
R>10
500
0.655 SWPC
1.0
400
0.8
250
SSN
1952-1990
200
y = 0.000017x3 - 0.008270x2 + 2.367415x - 119.487222
R2 = 0.993433
150
0.6
?
100
1996-2012
300
R
Something is
happening
with the Sun
50
200
F10.7
0
0.4
0
50
100
150
200
250
Observed Sunspot Number Divided by Synthetic SSN (1952-1990)
1.4
Spots per Group for Locarno
600
SIDC
1.2
0.2
0.0
R>10
R
14
500
0.655 SWPC
1.0
100
400
0.8
0.6
19
?
0.2
R
20
100
21
22
1975 1980
1985 1990
23
S/G
21
22
23
10
24
24
0
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
0.0
1950 1955
19
1960 1965
20
1970
12
300
R
200
0.4
(b)
8
0
1995
2000 2005
2010 2015
?
6
4
Spots per Group declining
SSN obs / SSN*
3.0
1975
1980
1985
1990
1995
2000
2005
2010
2
0
2015
SSN* = 54.7 MPSI 1.0089
2.5
2.0
5-month
running average
Magnetic Plage
Strength Index
Umbral Magnetic Field
4000
3500
Livingston & Penn
B
Gauss
3000
1.5
2500
1.0
2000
0.5
?
Year
0.0
1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015
?
1500
1000
1998
No visible spots form
2000
2002
2004
2006
2008
2010
2012 Year
We don’t know what causes this, but sunspots are becoming more difficult to see or not forming as they
used to. There is speculation that this may be what a Maunder-type minimum looks like: magnetic fields
still present [cosmic rays still modulated], but just not forming spots. If so, exciting times are ahead. 34
Perhaps like this:
Magnetic Field
Visible Light
2012-10-17
35
Conclusions
• The historical (official) ‘Wolf’ sunspot record has
been re-assessed and need revision
• The Group Sunspot Number is flawed and
should not be used anymore
• There likely was no Modern Grand Maximum
• The Cosmic Ray record calibration is uncertain
• The polar field precursor method for prediction
of a low solar cycle 24 has worked well
• The Sun may be entering a new regime of very
low activity
36