Prediction on Time-Scales of Years to Decades Discussion Group A
Sunspot Number and Solar Activity Sunspot Area 10.7cm Radio Flux GOES X-Ray Flares Total Irradiance Geomagnetic aa index Sunspot number is well correlated with some measures of solar activity. The long record of sunspot numbers helps to characterize the solar cycle. Feature recognition techniques may help to better characterize magnetic structures. Climax Cosmic-Ray Flux
Prediction Cycle 23 Prediction via Curve Fitting
Prediction Accuracy Cycle amplitude (and shape) are well determined 2-3 years after minimum.
Dynamos with Meridional Flow Dynamo models that incorporate a deep meridional flow to transport magnetic flux toward the equator at the base of the convection zone have predictive capabilities. Dikpati and Charbonneau, ApJ 518, 508-520, 1999
The Sun’s Magnetic Cycle Magnetic field maps show the equatorward drift of the active regions, Hale’s polarity law, differential rotation, and poleward meridional flow.
Flux-transport Dynamo-based Prediction Scheme The Meridional Flow “Magnetic persistence”, or the duration of the Sun’s “memory” of its own magnetic field, can be controlled by the meridional circulation.
Flux-transport Dynamo-based Prediction Scheme The Poloidal Source from Sunspot Areas The time-variation of the poloidal source function within each sunspot-cycle is derived from observations of the sunspot areas during that cycle.
Simulating sequence of cycles 12 through 23 and predicting cycle 24 23 20 18 19 12 13 14 16 21 22 17 15 24 23 20 18 19 12 13 14 16 21 22 17 15 Observed cycles • The Dynamo correctly pre-dicts the sequence of relative cycle peaks for cycles 16 through 23 (cycles 12-15 are used to build the Sun’s memory of its magnetic field). • Based on successful simu-lation of past cycle peaks , we predict that the peak amplitude of cycle 24 will be 1.2-1.5 times stronger than cycle 23 (Sunspot number ~150). Simulated solar cycles (N+S)
Polar Field Strength Polar field strength near the time of cycle minimum has been used by Schatten et al. and by Svalgaard, Cliver, and Kamide (2005) as an indicator of the strength of the following cycle. This suggests similar sizes for the last three cycles and a small amplitude (Rz ~ 75) for the next. If polar fields are the seeds for the n+2 cycle then cycle 24 should be like the last two and cycle 25 should be small.
Drift Rate – Period Anti-correlation The sunspot cycle period is anti-correlated with the drift velocity at cycle maximum. The faster the drift rate the shorter the period. This is also expected from dynamo models with deep meridional flow. R=-0.5 95% Significant
Drift Rate – Amplitude Correlations The drift velocity at cycle maximum is correlated to the amplitude of the second following (N+2) cycle. This is also predicted by dynamo models with deep meridional flow. It also provides a prediction for the amplitudes of future cycles. R=0.7 99% Significant
Cycle 24 Amplitude Prediction The fast drift rates at the maximum of the last (22nd) cycle (red oval – northern hemisphere, yellow oval – southern hemisphere) indicate a larger than average amplitude for the next cycle (24th).
Cycle 25 Amplitude Prediction The slow drift rates at the maximum of the current (23rd) cycle (red oval – northern hemisphere, yellow oval – southern hemisphere) indicate a much smaller than average amplitude for cycle 25 (2020 maximum).
Ice Core Nitrate Data of SPEs The Carrington Event of 1859
Distribution of SPEs over the Last Five Cycles SPEs roughly follow the cycle but with proportionally more late in the cycle and very significant variations from cycle-to-cycle.
Solar Cycle Modulation of GCRs 10Be measurements show that our recent experience with solar cycle modulation of GCRs might not be a good predictor of future levels.
Group A Conclusions • Solar activity predictions based on curve-fitting become reliable 2-3 years after sunspot minimum. • Solar cycle predictions 1-2 cycles in advance are now available from dynamo models that incorporate a meridional flow. Better measurements of the meridional flow are needed. • SPEs can occur at any time. Better characterization of large events require further investigation of ice core data. • 10Be measurements show that our recent experience with solar cycle modulation of GCRs might not be a good predictor of future levels. Better calibration of ice core data vis-à-vis neutron monitor data is needed.