Estimating the Size and Timing of the Maximum Amplitude of Solar Cycle 24

A simple statistical method is used to estimate the size and timing of maximum amplitude of the next solar cycle （cycle 24）. Presuming cycle 23 to be a short cycle （as is more likely）, the minimum of cycle 24 should occur about December 2006 （±2 months） and the maximum, around March 2011 （±9 months）, and the amplitude is 189.9 ± 15.5, if it is a fast riser, or about 136, if it is a slow riser. If we presume cycle 23 to be a long cycle （as is less likely）, the minimum of cycle 24 should occur about June 2008 （±2 months） and the maximum, about February 2013 （±8 months） and the maximum will be about 137 or 80, according as the cycle is a fast riser or a slow riser.

Association of CMEs with solar surface activity during the rise and maximum phases of solar cycles 23 and 24

The cyclical behaviors of sunspots, flares and coronal mass ejections （CMEs） for 54 months from 2008 November to 2013 April after the onset of Solar Cycle （SC） 24 are compared, for the first time, with those of SC 23 from 1996 November to 2001 April. The results are summarized below. （i） During the maximum phase, the number of sunspots in SC 24 is significantly smaller than that for SC 23 and the number of flares in SC 24 is comparable to that of SC 23. （ii） The number of CMEs in SC 24 is larger than that in SC 23 and the speed of CMEs in SC 24 is smaller than that of SC 23 during the maximum phase. We individually survey all the CMEs （1647 CMEs） from 2010 June to 2011 June. A total of 161 CMEs associated with so- lar surface activity events can be identified. About 45% of CMEs are associated with quiescent prominence eruptions, 27% of CMEs only with solar flares, 19% of CMEs with both active-region prominence eruptions and solar flares, and 9% of CMEs only with active-region prominence eruptions. Comparing the association of the CMEs and their source regions in SC 24 with that in SC 23, we notice that the characteristics of source regions for CMEs during SC 24 may be different from those of SC 23.

A cyclic behavior of CME accelerations for accelerating and decelerating events

We investigate the cyclic evolutionary behavior of CME accelerations for accelerating and decelerating CME events in cycle 23 from 1997 January to 2007 December. It is found that the absolute values of semiannual mean accelerations of both accelerating and decelerating CME events roughly wax and wane in a cycle, delaying the sunspot cycle in time phase. We also investigate the semiannual number of CMEs with positive and neg- ative acceleration and find that there are more decelerating CME events than accelerating CME events during the maximum period of a cycle （about three years）, but there are more accelerating CME events than decelerating CME events during the rest of the time interval of the cycle. Our results seem to suggest that the different driving mechanisms may be acting accelerate and decelerate CME events; for accelerating CME events, the propelling force （Fp） statistically seems to play a significant role in pushing CMEs outward; for decelerating CME events, the drag （Fd） statistically seems to play a more effective role in determining CME kinematic evolution in the outer corona. During the maximum period of a cycle, because of the V^2 dependence, Fd is generally stronger; because of the magnetic field dependence, Fp is also generally stronger. Thus, the absolute values of both the negative and positive accelerations are generally larger during that time. Because of the V^2 dependence, Fd may be more effective during the maximum period of a cycle. Hence, there are more decelerating CME events than accelerating CME events during that time. During the minimum time interval of a cycle, CMEs have relatively small speeds, and Fp may be more effective. Therefore, there are more accelerating CME events than decelerating CME events during that time.

Speed Distributions of CMEs in Cycle 23 at Low and High Latitudes

We analyzed the speed （v） distributions of 11584 coronal mass ejections （CMEs） observed by the Large Angle and Spectrometric Coronagraph Experiment on board the Solar and Heliospheric Observatory （SOHO/LASCO） in cycle 23 from 1996 to 2006. We find that the speed distributions for high-latitude （HL） and low-latitude （LL） CME events are nearly identical and to a good approximation they can be fitted with a lognormal distribution. This finding implies that statistically the same driving mechanism of a nonlinear nature is acting in both HL and LL CME events, and CMEs are intrinsically associated with the source＇s magnetic structure on large spatial scales. Statistically, the HL CMEs are slightly slower than the LL CMEs. For HL and LL CME events respectively, the speed distributions for accelerating and decelerating events are nearly identical and also to a good approximation they can be both fitted with a lognormal distribution, thus supplementing the results obtained by Yurchyshyn et al.

Periodicity in the most violent solar eruptions: recent observations of coronal mass ejections and flares revisited

Using the Hilbert-Huang Transform method, we investigate the periodic- ity in the monthly occurrence numbers and monthly mean energy of coronal mass ejections （CMEs） observed by the Large Angle and Spectrometric Coronagraph Experiment on board the Solar and Heliographic Observatory from 1999 March to 2009 December. We also investigate the periodicity in the monthly occurrence numbers of Hα flares and monthly mean flare indices from 1996 January to 2008 December. The results show the following. （1） The period of 5.66 yr is found to be statistically significant in the monthly occurrence numbers of CMEs; the period of 10.5 yr is found to be statistically significant in the monthly mean energy of CMEs. （2） The periods of 3.05 and 8.70 yr are found to be statistically significant in the monthly occurrence numbers of Hα flares; the period of 9.14 yr is found to be statistically significant in the monthly mean flare indices.