Predicting Solar Cycle 24 With Geomagnetic Precursors
Abstract
We describe using a geomagnetic precursor to predict the amplitude of the upcoming solar cycle. The amplitude prediction for Solar Cycle 24 is 65 +/- 20 in smoothed sunspot number, indicating a below-average amplitude for Solar Cycle 24. Four precursor peaks are seen in the decline of Solar Cycle 23. The earliest is the most prominent but coincides with large levels of non-recurrent geomagnetic activity associated with the Halloween storms. The second and third peaks are for smaller amplitudes and show that a weak cycle precursor closely following a period of strong solar activity may be difficult to resolve. A fourth peak, in early 2008, which has recurrent activity similar to precursors of earlier solar cycles and appears to be the ``true" precursor peak for Solar Cycle 24, predicts the smallest amplitude for Solar Cycle 24. Several effects contribute to the smaller prediction when compared to other geomagnetic precursor predictions. During Solar Cycle 23 the correlation between sunspot number and F10.7 shows that F10.7 is greater than the equivalent sunspot number over most of the cycle, implying the sunspot number underestimates the solar activity component. During 2003 the correlation between aa and Ap shows that aa is much greater than the value predicted from Ap, leading to an overestimate of the aa precursor for that year. But the most important effect is the lack of recurrent geomagnetic activity until 2008. We conclude that Solar Cycle 24 will be no stronger than average and could be much weaker than average.
- Publication:
-
AAS/Solar Physics Division Meeting #40
- Pub Date:
- May 2009
- Bibcode:
- 2009SPD....40.1105P