Longterm prediction of solar activity using the combined method

The Combined Method is a non-parametric regression technique for long-term prediction of smoothed monthly sunspot numbers. Starting from a solar minim um, a prediction of the succeeding maximum is obtained by using a dynamo-ba sed relation between the geomagnetic aa index and succeeding solar maxima. Then a series of predictions is calculated by computing the weighted averag e of past cycles of similar level. This technique leads to a good predictio n performance, particularly in the ascending phase of the solar cycle where purely statistical methods tend to be inaccurate. For cycle 23 the combine d method predicts a maximum of 160 (in terms of smoothed sunspot number) ea rly in the year 2000.