Sunday, September 13, 2015
The current prediction for Sunspot Cycle 24 gives a smoothed sunspot number (V2.0 maximum) of about 101 in late 2013. The smoothed sunspot number (V2.0) reached a peak of 116.4 in April 2014. This will probably become the official maximum.
This second peak surpassed the level of the first peak (98.3 in March 2012). Many cycles are double peaked but this is the first in which the second peak in sunspot number was larger than the first.
We are currently over seven years into Cycle 24. The current predicted and observed size makes this the smallest sunspot cycle since Cycle 14, which had a maximum smoothed sunspot number (V2.0) of 107.2 in February of 1906. (!!!)
Another indicator of the level of solar activity is the flux of radio emission from the Sun at a wavelength of 10.7 cm (2.8 GHz frequency). This flux has been measured daily since 1947. It is an important indicator of solar activity because it tends to follow the changes in the solar ultraviolet that influence the Earth's upper atmosphere and ionosphere. Many models of the upper atmosphere use the 10.7 cm flux (F10.7) as input to determine atmospheric densities and satellite drag. F10.7 has been shown to follow the sunspot number quite closely and similar prediction techniques can be used. Our predictions for F10.7 are available in a text file, as a Jpeg image, and as a pdf-file.