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The amplitude of a solar-activity cycle is found to be well correlated (r = −0.811) with the descending time three cycles earlier, in smoothed monthly-mean sunspot numbers for Cycles 8 – 23. The
descending time therefore can be used as one of the indicators to predict the amplitudes. As a result, the amplitudes of Cycles
24 – 25 are estimated to be 114.8 ± 17.4, 111.6 ± 17.4, respectively, where the error bar equals ± standard error. 相似文献
2.
Zhanle Du 《Solar physics》2011,273(1):231-253
The shape of each sunspot cycle is found to be well described by a modified Gaussian function with four parameters: peak size
A, peak timing t
m, width B, and asymmetry α. The four-parameter function can be further reduced to a two-parameter function by assuming that B and α are quadratic functions of t
m, computed from the starting time (T
0). It is found that the shape can be better fitted by the four-parameter function, while the remaining behavior of the cycle
can be better predicted by the two-parameter function when using the data from a few (about two) months after the starting
time defined by the smoothed monthly mean sunspot numbers. As a new solar cycle is ongoing, its remaining behavior can be
constructed by the above four- or two-parameter function. A running test shows that the maximum amplitude of the cycle can
be predicted to within 15% at about 25 months into the cycle based on the two-parameter function. A preliminary modeling to
the first 24 months of data available for the current cycle indicates that the peak of cycle 24 may probably occur around
June 2013±7 months with a size of 72±11. The above results are compared to those by quasi-Planck functions. 相似文献
3.
The correlation coefficient (r) between the maximum amplitude (R
m) of a sunspot cycle and the preceding minimum aa geomagnetic index (aa
min), in terms of geomagnetic cycle, can be fitted by a sinusoidal function with a four-cycle periodicity superimposed on a declining
trend. The prediction index (χ) of the prediction error relative to its estimated uncertainty based on a geomagnetic precursor method can be fitted by a
sinusoidal function with a four-and-half-cycle periodicity. A revised prediction relationship is found between the two quantities:
χ<1.2 if r varies in a rising trend, and χ>1.2 if r varies in a declining trend. The prediction accuracy of R
m depends on the long-term variation in the correlation. These results indicate that the prediction for the next cycle inferred
from this method, R
m(24)=87±23 regarding the 75% level of confidence (1.2-σ), is likely to fail. When using another predictor of sunspot area instead of the geomagnetic index, similar results can be
also obtained. Dynamo models will have better predictive powers when having considered the long-term periodicities. 相似文献
4.
Zhanle Du 《Solar physics》2012,278(1):203-215
Smoothed monthly mean coronal mass ejection (CME) parameters (speed, acceleration, central position angle, angular width, mass, and kinetic energy) for Cycle 23 are cross-analyzed, showing that there is a high correlation between most of them. The CME acceleration (a) is highly correlated with the reciprocal of its mass (M), with a correlation coefficient r=0.899. The force (Ma) to drive a CME is found to be well anti-correlated with the sunspot number (R z), r=?0.750. The relationships between CME parameters and R z can be well described by an integral response model with a decay time scale of about 11 months. The correlation coefficients of CME parameters with the reconstructed series based on this model (\(\overline{r}_{\mathrm{f1}}=0.886\)) are higher than the linear correlation coefficients of the parameters with R z (\(\overline{r}_{\mathrm{0}}=0.830\)). If a double decay integral response model is used (with two decay time scales of about 6 and 60 months), the correlations between CME parameters and R z improve (\(\overline{r}_{\mathrm{f2}}=0.906\)). The time delays between CME parameters with respect to R z are also well predicted by this model (19/22=86%); the average time delays are 19 months for the reconstructed and 22 months for the original time series. The model implies that CMEs are related to the accumulation of solar magnetic energy. These relationships can help in understanding the mechanisms at work during the solar cycle. 相似文献
5.
The running cross-correlation coefficient between solar-cycle amplitudes and rise times at a certain cycle lag is found to
vary in time, when using the smoothed monthly-mean sunspot group numbers available for 1610 – 1995. It may be negative or
positive for different periods of time. The Waldmeier effect (in which the rise times decrease with amplitude) is also found
to be very weak for some cycles. This result represents an observational constraint on solar-dynamo models and can help us
better understand the long-term evolution of solar activity. 相似文献
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