Using the Modified Precursor Method to Estimate the Size of Cycle 24

Modified geomagnetic precursor techniques for predicting the size of the following sunspot cycle are developed, where these techniques use the 12-month moving averages of the number of disturbed days (when Ap greater than or equals 25), the Ap index, the aa index, and the aaI index at about 4 yr during the declining portion of the preceding sunspot cycle. For cycle 24, these techniques suggest that its RM will measure about 130 +/- 14, a value outside the consensus prediction interval of the low prediction (90 +/- 10) given by the NOAA Solar Cycle 24 Prediction Panel. Furthermore, cycle 24 is predicted to be a fast-rising cycle (ASC = 44 +/- 5 months), peaking before April 2012, presuming the official start of cycle 24 in March 2008. Also discussed are the variation of solar cycle lengths and Hale cycle effects, as related to cycles 23 and 24.