太阳总辐照的演化特征分析

太阳总辐照在23和24太阳活动周的显著周期分别为35 d和26 d,进而推断太阳的准旋转周期在23和24太阳活动周也分别为35 d和26 d.太阳总辐照在24周极小期的值可能与蒙德极小期的值相近.在一个太阳旋转周到几个月的时间尺度上,太阳黑子是引起太阳总辐照变化的主要原因,但不是唯一的原因;在几天到一个太阳旋转周的时间尺度上,太阳总辐照的变化与MgⅡ特征指数是不相关的.     

太阳表面磁场的分布与演化研究进展

太阳磁场、较差自转和内部对流使得日面磁场与磁活动在很大的时间尺度和空间尺度范围均表现得相当复杂.其中最有名的是太阳活动的11年周期,或22年磁周期.在较小时间尺度上,从几秒到几小时,有时太阳大气中会发生一些壮观的爆发事件,如耀斑、日珥爆发、日冕物质抛射等.所有这些形式的事件都与太阳磁场紧密关联.简单评述了太阳磁场起源与观测方法,重点论述了不同尺度太阳磁场的空间分布与演化,介绍了从太阳磁活动现象统计得到的有关太阳磁场的几个典型特征,同时讨论了进一步研究的方向.     

太阳物理前沿的新进展

本文就近年来太阳物理前沿课题中以下5个方面的主要进展作一简要的综述;(1)太阳观测仪器;(2)耀斑物理研究;(3)太阳磁场的观测和研究;(4)太阳上各种振荡的观测和研究;(5)太阳活动周期的研究。此外,对今后的发展趋势和展望也进行了讨论。     

太阳黑子的世纪周期及对24、25活动周的预报

太阳活动除了具有公认的11 a周期以外,还存在着一个80～120 a变化的世纪周期,也称为Gleissberg周期.使用傅里叶变换和小波分析的方法,分析了1700～2008年的年均黑子数世纪周期的变化规律.得到结果:在太阳活动世纪周期的低谷期,所对应11 a太阳周的极大年和极小年的黑子数目都比其他太阳周的低.在这300多年里,世纪周期的周期长度也有变化.由世纪周期的变化趋势,预测第24、25太阳活动周将处于世纪周期的低谷期.通过对以前3个世纪周期的谷期黑子数求平均的方法,得到第24,25太阳周极大年年均黑子数为63.6±21.1,极小年的为2.2±2.1.这些结果有助于理解当前太阳活动反常宁静这一现象.     

太阳磁场和速度场的研究

本文介绍了怀柔太阳学术集团于２２ 太阳周期间在太阳磁场和速度场研究方面的部分成果及对２３ 太阳活动周工作的展望     

22周上升相日面各经度带的活动规律

本文回顾了１９８３年以来的一些对太阳活动的谱分析结果，大致可分为两种规律；在太阳活动１１年周期的上升相一般呈现８０天左右的周期。下降相呈现１５０天左右的周期。这些规律均是由太阳全日面总体活动指数得到的谱分析结果。     

太阳活动与太阳自转速率变化关系的分析

研究发现,太阳自转速率的变化与太阳活动之间存在一定的联系,但是不同学者的研究结论存在着矛盾:有的认为两者为正相关,而有的却认为是负相关.究竟两者之间是什么关系,需要做进一步深入的分析.利用EEMD (Ensemble Empirical Mode Decomposition)等方法对太阳自转速率和太阳黑子数据序列进行相关关系以及相位关系的计算和分析,以探讨太阳自转速率变化与太阳活动之间的关系.研究发现:两者的长期趋势项分量呈显著负相关;在11 yr左右周期分量上,观测到的太阳自转速率滞后太阳黑子的变化约2 yr时,呈显著负相关关系,超前3 yr时呈现次显著的正相关;对太阳活动第12–23周各周内部太阳黑子与太阳自转速率的相关分析表明,两者的关系比较复杂,但负相关关系更为显著.这为进一步理解太阳活动变化与太阳自转速率变化之间的成因联系提供了新的依据.     

22周上升相日面各经度带的活动规律

本文回顾了１９８３年以来一些对太阳活动的谱分析结果。大致可分为两种规律：在太阳活动１１年周期的上升相一般呈现８０天左右的周期。下降相呈现１５０天左右的周期。这些规律均是由太阳全日面总体活动指数得到的谱分析结果。文中将第２２周上升段（１９８７．１．１—１９８８．７．３１）的太阳黑子群和Ｘ射线耀斑按经度带作了极大熵谱估计。结果表明，各经度带的活动规律不同，同一经度带内，太阳黑子群和Ｘ射线耀斑的出现规律也不尽相同。这种将事件按经度带分布得到的活动规律对事件本身的中期预报将会有实际应用价值。     

太阳中微子流变化的周期性与太阳活动

本文对1970年到1979年的太阳中微子流和太阳活动(太阳黑子、耀斑和质子事件)的数据作最大熵谱分析,并求其互相关函数和初相,得到:太阳中微子流和太阳活动均有11年的长周期;太阳中微子流和太阳质子事件还有共同的近3年、2年和1年左右的周期。太阳中微子流的3年周期占支配地位,质子事件中的3年周期亦占有重要地位。二级以上的耀斑事件亦有近两年的周期。它们的互相关函数和初相表明:太阳中微子流与太阳活动有正相关;对近11年周期的数据,太阳黑子和太阳耀斑相对于太阳中微子均有延迟时间47个月,对质子事件有延迟时间41个月。对于约3年的周期,质子的延迟时间为10个月。结合他人的太阳半径和太阳磁场的测量与分析结果,得到一个符合标准太阳模型中物理过程的太阳中微子流变化与太阳活动间的因果关系,并对这个因果关系的可能机制进行了讨论。     

太阳黑子周极小年的统计性质——兼论第22周起始极小是否已经出现

探讨太阳周极小年的性质关系到确定极小值的位置及太阳周的长度,从而与太阳活动周的研究、太阳活动预报及水文、气象等地球物理现象的研究密切相关.当前对第22黑子周特征值的预报相当弥散,第22周起始极小是否已经出现的问题受到普遍关注.不同的太阳活动指标达到极值的时间不同,一般以太阳黑子数月均平滑最低值的位置来定义极小年.     

Short-Term Periodicity in Solar Mean Magnetic Field during Activity Maximum and Minimum Periods

The short-term periodicity in the solar mean magnetic field (SMMF) observed at the Wilcox Solar Observatory during the last four activity cycles is investigated by using Lomb?CScargle periodograms. Our results show that the SMMF has main periods of about 27, 13.5, and 9 days in both the maximum and minimum years of each activity cycle. The SMMF has the most dominant period of about 27 days during the activity maxima. However, during the activity minimum years the 13.5-day periodicity is the most significant, except for the minimum of 1984??C?1986. These results indicate that the distribution of active regions in the activity maximum years is quite different from that in the minimum years.     

A Study of the Periodic Variations of Solar Magnetic Fields During Maxima and Minima of Solar Activity

By using the solar magnetic ?eld data of Wilcox Observatory from 1975 to 2010, the short-time periodicities of solar mean magnetic ?elds during solar maximum and minimum years are analyzed. The results reveal that the solar magnetic ?elds mainly exhibit the approximate periods of 9 d, 13 d, and 27 d. During maximal solar activity the period about 27 d is most conspicuous, while during minimal solar activity the most evident period is approximately 13.5 d (except the solar minimum in the years 1984-1986). These results imply that solar active regions exhibit evidently different distributions in the periods of maxima and minima of solar activity.     

Cyclic Changes in Solar Rotation Inferred From Temporal Changes in the Mean Magnetic Field

Time–frequency variability of the solar mean magnetic field (SMMF) was studied, based on a continuous wavelet analysis. The rotational modulation of the SMMF dominates the wavelet spectrum at 27–30 and 13.5-day time scales. The rotational variation, in turn, is amplitude-modulated by the quasi-biennial periodicity in the SMMF. This is caused by magnetic field eruptions. Rigidly rotating modes appear in the time–longitude distribution of the large-scale magnetic field that is plotted from a deconvolution of the SMMF time series with a Carrington period. These rotational modes coexist and transform into one another over an 11-yr cycle. The modes with periods of 27.8–28.0 days dominate the phase of activity rise, whereas the 27-day rotational mode dominates the declining phase of the 11-yr cycle. The rotational modes with periods of 29–30 days occurred episodically. Most of the features in the time–longitude distribution of the SMMF are identifiable with those in similar diagrams of the solar background magnetic fields. They represent a combined effect of the background magnetic fields from both hemispheres. Eruptions of magnetic fields lead to dramatic changes in the picture of solar rotation and correlate well with the polarity asymmetry in the SMMF signal. The polarity asymmetry in the SMMF time series exhibits both long-term changes and a 22-yr cyclic behaviour, depending on the reversals of the global magnetic field in cycles 20–23.     

太阳活动周期的小波分析

运用小波技术对太阳射电流量2800 MHz,太阳黑子数和太阳黑子面积数周期进行分析．其结果表明: (1)这3个系列的数据显示最显著的周期是10．69年,其他周期并不明显．(2)小波功率谱给出了全部时间-周期范围的功率谱变化,它显示了在某个周期处于某个时段的局部功率的变化,小波功率谱分析表明,小于1年的周期仅仅在太阳活动最大期附近比较明显．(3)太阳射电2800 MHz,太阳黑子数和太阳黑子面积数的几个周期(10．69年,5．11年, 155．5天)的小波功率谱比较相似,出现峰值的时间相同;曲线的起伏相似,周期越小,曲线起伏的频率越大．     

Periodicity in the Basal Component of Radio Emission During Maximum and Minimum Solar Activity

The basal component of radio emission is the radio intensity obtained after subtracting the sunspot-dependent (magneto-active) component from the observed flux and finally deducting the steady part from this subtracted value. The periodicity of this basal component of solar radio emission in the frequency band 0.245–15.4 GHz was studied both for the solar maximum (1980 and 1991) and minimum (1975 and 1986) periods. A constant periodicity of 35 days was observed in the entire radio band under study during the periods of maximum solar activity, whereas the periodicity fluctuates harmonically with frequency during the minimum periods, giving rise to an average time period of approximately 54 days.     

太阳光球磁通量南北不对称性研究

运用统计方法系统研究了1978-2002年太阳光球磁通量南北不对称性变化特征，发现其与太阳活动周有关．不对称值在太阳活动极小年要明显高于太阳活动极大年，并且磁通量变化总是由上升段的北半球占优逐渐过渡到下降段的南半球占优．另外运用小波变换方法详细讨论了这种不对称性变化可能存在的周期信息．     

Solar Rotational Periodicities and the Semiannual Variation in the Solar Wind, Radiation Belt, and Aurora

The behavior of a number of solar wind, radiation belt, auroral and geomagnetic parameters is examined during the recent extended solar minimum and previous solar cycles, covering the period from January 1972 to July 2010. This period includes most of the solar minimum between Cycles 23 and 24, which was more extended than recent solar minima, with historically low values of most of these parameters in 2009. Solar rotational periodicities from 5 to 27 days were found from daily averages over 81 days for the parameters. There were very strong 9-day periodicities in many variables in 2005?–?2008, triggered by recurring corotating high-speed streams (HSS). All rotational amplitudes were relatively large in the descending and early minimum phases of the solar cycle, when HSS are the predominant solar wind structures. There were minima in the amplitudes of all solar rotational periodicities near the end of each solar minimum, as well as at the start of the reversal of the solar magnetic field polarity at solar maximum (～?1980, ～?1990, and ～?2001) when the occurrence frequency of HSS is relatively low. Semiannual equinoctial periodicities, which were relatively strong in the 1995?–?1997 solar minimum, were found to be primarily the result of the changing amplitudes of the 13.5- and 27-day periodicities, where 13.5-day amplitudes were better correlated with heliospheric daily observations and 27-day amplitudes correlated better with Earth-based daily observations. The equinoctial rotational amplitudes of the Earth-based parameters were probably enhanced by a combination of the Russell-McPherron effect and a reduction in the solar wind-magnetosphere coupling efficiency during solstices. The rotational amplitudes were cross-correlated with each other, where the 27-day amplitudes showed some of the weakest cross-correlations. The rotational amplitudes of the >?2 MeV radiation belt electron number fluxes were progressively weaker from 27- to 5-day periods, showing that processes in the magnetosphere act as a low-pass filter between the solar wind and the radiation belt. The A _p/K _p magnetic currents observed at subauroral latitudes are sensitive to proton auroral precipitation, especially for 9-day and shorter periods, while the A _p/K _p currents are governed by electron auroral precipitation for 13.5- and 27-day periodicities.     

Evolutionary Characteristics of Total Solar Irradiance

The significant periods of total solar irradiance are 35 d and 26 d in the 23rd and 24th solar activity cycles, respectively. It is inferred that the solar quasi-rotation periods are also 35 d and 26 d in the 23rd and 24th solar activity cycles, respectively. The value of total solar irradiance around the 24th solar activity minimum may be close to the value of Maunder minimum. On the timescales from one solar rotation period to several months, sunspots are the main reason to cause the variation of total solar irradiance, but not the unique one, and the variation of total solar irradiance are not correlated with the Mg II index on the timescales from a few days to one solar rotation period.     

Thirteen-day periodicity and the center-to-limb dependence of UV,EUV, and X-ray emission of solar activity

Periodicity in the 13–14 day range for full-disk UV fluxes comes mainly from episodes of solar activity with two peaks per rotation, produced by the solar rotational modulation from two groups of active regions roughly 180° apart in solar longitude. Thirteen-day periodicity is quite strong relative to the 27-day periodicity for the solar UV flux at most wavelengths in the 1750–2900 Å range, because the rapid decrease in UV plage emission on average with increasing solar central angle shapes the UV variations for two peaks per rotation into nearly a 13-day sinusoid, with deep minima when the main groups of active regions are near the limb. Chromospheric EUV lines and ground-based chromospheric indices have moderate 13-day periodicity, where the slightly greater emission of regions near the limbs causes a lower strength relative to the 27-day variations than in the above UV case. The lack of 13-day periodicity in the solar 10.7 cm flux is caused by its broad central angle dependence that averages out the 13-day variations and produces nearly sinusoidal 27-day variations. Optically thin full-disk soft X-rays can have 13-day periodicity out of phase with that of the UV flux because the X-ray emission peaks when both groups of active regions are within view, one group at each limb, when the optically thick UV flux is at a rotational minimum. The lack of 13-day periodicity in the strong coronal lines of Fexv at 284 Å and Fexvi at 335 Å during episodes of 13-day periodicity in UV and soft X-ray fluxes shows that the active region emission in these strong lines is not optically thin; resonant scattering is suggested to cause an effective optical depth near unity in these hot coronal lines for active regions near the limb.     

Features of the Solar Active Cycles

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