Predicting the maximum sunspot number and the associated geomagnetic activity indices aa and Ap for solar cycle 25

Over the last three solar cycles, the precursor method has proven to be a very reliable technique for forecasting ensuing solar cycles. In the present work, we have used the geomagnetic activity indices: aa and Ap measured during the last 4 years of the descending phase of solar activity cycles as precursors for predicting the strength of the next solar cycle 25. From the indices aa and Ap, we estimate the maximum sunspot number (SSN) amplitude of the upcoming solar cycle i.e., solar activity cycle 25 to be 119.42 +/- 28.41 and 113.70 +/- 23.51, respectively. This suggests that the activity of the next solar cycle 25 is likely to be comparable to that of cycle 24. The results further suggest that this forecast of the maximum SSN will be associated with the values aa = 16.67 +/- 3.11 nT and Ap = 8.78 +/- 2.34 nT. This indicates that the maximum solar cycle 25 is expected to be accompanied by higher geomagnetic activity levels than in cycle 24, but less than those in the previous cycles 22 and 23. Predicting the level of solar activity is of particular interest because it enhances understanding on establishing a consistent picture of the solar dynamo process and changes in the magnetic field therein; and also helps us in taking decisions having implications in our operational technological capability in space.