Cycle 24: The Continuing Deviation
Between the Sunspot Number and
F10.7 Activity Indices
Ken Tapping
Ken.Tapping@nrc-cnrc.gc.ca
Per SORCE 2011
• Compared observed values of F10.7 with a sunspotnumber based proxy.
• These two indices are usually highly-correlated, to the
point where one can be used as a proxy for the other.
• Soon after the maximum of Cycle 23, there started a
growing excess of F10.7 over the value that would have
been expected on the basis of sunspot number.
• There followed the extended minimum before the start of
Cycle 24 as identified by sunspot number and F10.7.
• This presentation is an update on the deviation between
sunspot number and F10.7.
450
Note that in the extended minimum,
sunspot numbers got very low
compared with F10.7.
400
F10.7 (red) and Ns (black)
350
Ns
F10.7
300
250
200
150
100
50
0
1940
1950
1960
1970
1980
Year
1990
2000
2010
2020
300
F10.7 ( proxy) 0.456N S 1 exp( 0.019Ns)
250
67
Cycle 23
F10.7
200
150
100
xt
1 t 90
xj
181 j t 90
50
0
50
100
150
Sunspot Number
200
250
0.2
0.15
0.1
P10.7
0.456N S 1 exp( 0.019Ns)
( ) 2
67
observed proxy
observed proxy
361-Day Running Average
0.05
0
-0.05
-0.1
-0.15
1945
1950
1955
1960
1965
1970
1975
1980
Year
1985
1990
1995
2000
2005
2010
0.2
0.15
Cycle 23
0.1
Cycle 24
0.05
0
-0.05
-0.1
-0.15
0
50
100
Mean Sunspot Number
150
200
Updated to include Data to August,
2012
• Data smoothed by a 361 or 181-day
running mean.
• Plots updated but nothing changed other
than adding more labels as needed.
300
F10.7 ( proxy) 0.456N S 1 exp( 0.019Ns)
250
67
Cycle 22
Cycle 23
F10.7
200
Cycle 24
150
100
x
1 t 90
xj
181 j t 90
50
0
50
100
150
Sunspot Number
200
250
0.2
P10.7
0.15
0.456N S 1 exp( 0.019Ns)
F10.7
( ) 2
F10.7
67
P10.7
P10.7
0.1
0.05
0
-0.05
20
-0.1
-0.15
1940
21
23
24
361-Day Running Average
1950
1960
1970
1980
Year
1990
2000
2010
2020
0.2
361-Day Running Average
0.15
C18
C19
C20
C21
C22
C23
C24
Cycle 23
Cycle 24
0.1
Cycle 21
Cycle 22
0.05
Cycle 19
0
-0.05
-0.1
-0.15
0
50
100
150
Sunspot Number
200
250
0.3
0.25
0.2
P10.7
0.456N S 1 exp( 0.019Ns)
F10.7
( ) 2
F10.7
67
P10.7
P10.7
0.15
0.1
0.05
0
-0.05
-0.1
-0.15
1940
20
21
23
24
181-Day Running Average
1950
1960
1970
1980
Year
1990
2000
2010
2020
0.3
181-Day Running Average
0.25
C18
C19
C20
C21
C22
C23
C24
Cycle 23
Cycle 24
0.2
0.15
Cycle 22
0.1
0.05
0
-0.05
-0.1
-0.15
0
50
100
150
Sunspot
Number
Year
200
250
Conclusions?
• F10.7 and sunspot number are usually highly-correlated, to the point
where one can be used as a proxy for the other.
• Soon after the maximum of Cycle 23, there started a growing excess
of F10.7 over the value that would have been expected on the basis
of sunspot number.
• There followed the extended minimum before the start of Cycle 24
as identified by sunspot number and F10.7.
• Is Cycle 24 still weird, or is it hinting that Cycle 25 is going to be
really weird?
• During previous extended minima some sort of activity was going
on, which was not reflected in the sunspot number record. Is that
what we are getting hints of now?
• Short-lived deficits in sunspot number compared with F10.7 occurred
in previous cycles, progressively getting bigger.