Large Spike in Cycle 24 Sunspots and F10.7 Solar Flux

Solar Cycle 24 still has some surprises.   Both the NOAA  Sunspot count and F10.7 solar flux spiked.  The right hand side of the chart below, from Solen  shows the Sunspot count to have peaked at about 120 and the F10.7 solar flux above  130.  Sunspot count and Solar Flux usually act in unison. Dr Svalgaard says that F10,7 is a more reliable indicator of solar activity than Sunspots

Last major update issued on September 6, 2017 at 05:00 UT. Update posted at 13:50 UT

The generally accepted  way to portray  Sunspots is using a smoothed count from Sunspot Index and Long-term Solar Observations (SILSO). SILSO data is provided by the  Royal Observatory of Belgium, in Brussels. That number is charted below as Ri smoothed. ” Smoothed” is the process of averaging the daily numbers over some period of time. Silso number uses a formula* (see below) that incorporates some 13 months of monthly data.

In the chart  below, Ri is the total monthly Sunspots that were occasioned by the solar polar fields,  north (Rnorth ) and south (Rsouth).

Spikes in activity are not  uncommon as can be seen in the above chart which chronicles Solar Cycle 24 from its beginning to the current time.  I am still surprised at this late date.


*The Silso formula:

The smoothed count is a 13-month averaged sunspot count using this Belgium’s formula:
Rs= (0.5 Rm-6 + Rm-5 + Rm-4 + Rm-3 + Rm-2 + Rm-1 + Rm + Rm+1 + Rm+2 + Rm+3 + Rm+4 + Rm+5 + 0.5 Rm+6 ) / 12
Rs = smoothed monthly sunspot count
Rm = One month’s actual sunspot count
The “-6” through “+6” appended to each Rm is the number of months before or after the month whose smoothed count is being calculated. The beginning and ending months in the formula are only given half the value of the others.*

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