Solar Cycle Ap Progression Page

Ap Progression

An initial ISES Solar Cycle 24 Prediction was released in April, 2007. At that time, the panel charged with determining the prediction was unable to agree on a single solution and provided two predictions. As of May, 2009 the panel has reached consensus on a single prediction for Solar Cycle 24. It is the lower of the two predictions previously issued.

The Solar Cycle products are updated once a month and are put on-line the first Tuesday after the new values are available. The latest values are usually available on the 3rd of every month. The Ap Geomagnetic Index is the preliminary estimate calculated by the United States Air Force (USAF). Smooth values are an average of 13 monthly observed values centered on the month of concern (the 1st and 13th months are given a weight of 0.5). Ap(avg)=(0.5*Ap(1) +1.0*Ap(2) +1.0*Ap(3)+ ... +1.0*Ap(12) +0.5*Ap(13))/12.0