Solar Cycle 24 September 13 Update

The International Sunspot number for September dropped to 37 from 66 in August.    The F10.7cm solar flux moved downward as well from 115 in August to 103 in September.   Both are measures of Solar activity.  Again, Solar Cycle 24 is decidedly less active than recent Solar Cycles. (Click on the charts to improve clarity.  All charts are  by “Solar Terrestrial Activity Report”).


This chart, from Solen etc, is interesting.  The black line labled Ri is the International Sunspot number. The Rnorth indicates the number of Sunspots that were counted in the Sun’s northern hemisphere and Rsouth those formed in the southern hemisphere. Rnorth plus Rsouth equal Ri.  Rnorth peaked in late 2011 at about 97 Sunspots.  Rsouth peaked at about 50  in the middle of  last year.  The smoothed number is the official count.  The smoothed number is calculated by doing a 13 month average from the numbers that lag 6 months behind the current month.  The maximum smoothed number for Cycle 24 so far is 66.9 which occurred in early 2012.  Most of the solar cycle experts believe that will be the maximum for Cycle 24.

Below is the solar polar field strength chart updated for September showing the south and north poles have both crossed the  Sun’s equator.  It is suggested that you read the discussion regarding solar polar fields by clicking on this Forecasting Solar Cycle 25 Using The Solar Polar Field Strength”.


This chart puts Cycle 24 in perspective with Cycle 23.


The projected Sunspot number, shown in green, is also a 13 month average but it has no six month delay built into the calculation.


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