Sunspot Number Progression
F10.7cm Radio Flux Progression
AP Progression
The recent Solar Cycle is represented in several ways. At the top is the Sunspot Number, in the middle, the F10.7cm Radio Flux, and at the bottom, the Ap Index (a measure of geomagnetic activity) history.
In all of the plots, the black line represents the monthly averaged data and the blue line represents a 13-month smoothed version of the monthly averaged data. For the Sunspot Number and F10.7cm, the forecast for the rest of the solar cycle is given by the red line.
Solar cycle predictions are used by various agencies and many industry groups. The solar cycle is important for determining the lifetime of satellites in low-Earth orbit, as the drag on the satellites correlates with the solar cycle, especially as represented by F10.7cm. A higher solar maximum decreases satellite life and a lower solar maximum extends satellite life. Also, the prediction gives a rough idea of the frequency of space weather storms of all types, from radio blackouts to geomagnetic storms to radiation storms, so is used by many industries to gauge the expected impact of space weather in the coming years.
The forecast comes from the Solar Cycle Prediction Panel representing NOAA, the International Space Environmental Services (ISES), and NASA. This amounts to the ‘official’ forecast for the solar cycle. The Prediction Panel forecasts the sunspot number expected for solar maximum and had predicted a maximum of 90 occurring in May, 2013. While awaiting final confirmation, all evidence points to the most recent solar maximum having peaked at 82 in April, 2014. This was within the expected range for the peak, but occurred significantly later than predicted.
The original Solar Cycle Prediction Panel forecasts (2009) and the April 2007 Press Release are available.