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The RI12 is the sunspot index smoothed over 12 months, which depicts, amongst other things, the cyclic behaviour of the solar activity. The index is available since 1749. The RI12 index is presently deduced from daily observations of about fifty observatories (see SIDC).

RIm are monthly values. Here is given the prediction of the ascending phase of cycle 24 using the McNish and Lincoln method. The maximum of the present solar cycle, in terms of smooth Ri index, is forseen to occur in 2013.

Ref. McNish, A. G. and Lincoln, J. Y.: 1949, Transactions American Geophysical Union 30, 673.

The blue bars are calculated monthly mean values and the orange dash line is the running average over 12 months. Red and orange bars are predicted values. Orange ones are anterior to the date when the prediction was computed (delay of 6 months because of the running average calculation).