太阳10.7 cm射电辐射流量预报方法初探

引进“相似周”方法,通过两种方式对第23周太阳10.7cm辐射流量（F10.7）月均值进行预报和预报,由“相似周”方法得到的第23周太阳黑子数月均平滑预测值来预测F10.7月均值和直接采用“相似周”方法对F10.7月均平滑值进行预测,通过对两种预报试验结果分析,得到以下结论。（1）两种预测结果与实际都比较吻合,都得到双峰结构。（2）直接通过相似周预测的F10.7的月均值结果较间接通过太阳黑子数的预测结果所推断的F10.7预测结果更接近实际观测结果。（3）使用“相似周”,预报方法,可以给出F10.7比较精细的剖面结构,这是其他普通预报方法很难做到的。     

第21～24太阳周4类空间天气事件爆发特征统计分析

对第21～24太阳周不同等级的太阳X射线耀斑事件、太阳质子事件、地磁暴事件及高能电子增强事件的爆发频次特征进行统计,结果表明:太阳周耀斑爆发的总数量与该太阳周的黑子数峰值呈正比,耀斑总数、X级耀斑事件数与峰值的相关系数分别为0.974,0.997;太阳质子事件主要发生在峰年前后1～2年,约占总发生次数的80%,峰值通量大于10pfu （1 pfu=1 cm-2·sr-1·s-1）的质子事件中,84%伴有耀斑爆发,并且主要伴随M或X级耀斑,少量伴随C级耀斑,峰值通量大于1000pfu的质子事件中,98%伴随M或X级耀斑,并且以X级耀斑为主;第21,22,23和24太阳周发生地磁暴最频繁的时间分别在1982,1991,2003年和2015年,分别滞后黑子数峰值时间3年、2年、2年和1年;72%的高能电子增强事件发生在太阳周下降期,24%的高能电子增强事件发生在太阳周上升期.      

利用相似周方法预测第24活动周开始时间

利用相似周方法对第24活动周的开始时间与第23活动周下降相后期的太阳黑子数进行了预报.根据第23周已经出现的特征参量和下降相的形态特征,选取9,10,11,15,17和20等六个太阳活动周作为第23周下降相的相似周,对第24周开始时间进行预报.预报结果显示,第24活动周的开始时间为2007年5±1月,黑子数平滑月均极小值为7.1±2.6,第23太阳活动周长度为11.1年.与其他研究者的预报结果相比较,本文给出的结果与文献[11]和[12]及MSFC的结果比较一致.通过对相似周方法在下降相预测太阳活动周结束时间的研究讨论,及对第23周上升阶段的太阳黑子数和F10.7平滑月均值预报结果的评估,可以看出,相似周预报方法在太阳活动周长期预报中是很有应用价值的.      

Analysis of ionospheric TEC response to solar and geomagnetic activities at different solar activity stages

Studying the relationship of total electron content (TEC) to solar or geomagnetic activities at different solar activity stages can provide a reference for ionospheric modeling and prediction. On the basis of solar activity indices, geomagnetic activity parameters, and ionospheric TEC data at different solar activity stages, this study analyzes the overall variation relationships of solar and geomagnetic activities with ionospheric TEC, the characteristics of the quasi-27-day periodic oscillations of the three variables at different stages, and the delayed TEC response of solar activity by conducting correlation analysis, Butterworth band-pass filtering, Fourier transform, and time lag analysis. The following results are obtained. (1) TEC exhibits a significant linear relationship with solar activity at different solar activity stages. The correlation coefficients |R| are arranged as follows: |R|_EUV > |R|_F10.7 > |R|sunspot number. No significant linear relationship exists between TEC and geomagnetic activity parameters (|R| < 0.35). (2) TEC, solar activity indices, and geomagnetic activity parameters have a period of 10.5 years. The maximum amplitudes of the Fourier spectrum for TEC and solar activity indices are nearly 27 days and those of geomagnetic activity parameters are nearly 27 and 13.5 days. (3) The deviations of the quasi-27-day significant periodic oscillation of TEC and solar activity indices are consistent. (4) No evident relationship exists between the quasi-27-day periodic oscillation of TEC and geomagnetic activity parameters. (5) The delay time of TEC for the 10.7 cm solar radio flux and extreme ultraviolet is always consistent, whereas that for sunspot number varies at each stage.     

Predicting indices of the ionosphere response to solar activity for the ascending phase of the 25th solar cycle

The international reference ionosphere, IRI, and its extension to plasmasphere, IRI-Plas, models require reliable prediction of solar and ionospheric proxy indices of solar activity for nowcasting and forecasting of the ionosphere parameters. It is shown that IRI prediction errors could increase for the F2 layer critical frequency foF2 and the peak height hmF2 due to erroneous predictions of the ionospheric global IG index and the international sunspot number SSN1 index on which IRI and IRI-Plas models are built. Regression relation is introduced to produce daily SSN1 proxy index from new time series SSN2 index provided from June 2015, after recalibration of sunspots data. To avoid extra errors of the ionosphere model a new solar activity prediction (SAP) model for the ascending part of the solar cycle SC25 is proposed which expresses analytically the SSN1 proxy index and the 10.7-cm radio flux F10.7 index in terms of the phase of the solar cycle, Φ. SAP model is based on monthly indices observed during the descending part of SC24 complemented with forecast of time and amplitude for SC25 peak. The strength of SC25 is predicted to be less than that of SC24 as shown with their amplitudes for eight types of indices driving IRI-Plas model.     

Geomagnetic activity associated with magnetic clouds,magnetic cloud-like structures and interplanetary shocks for the period 1995–2003

Using nine years (1995–2003) of solar wind plasma and magnetic field data, solar sunspot number, and geomagnetic activity data, we investigated the geomagnetic activity associated with magnetic clouds (MCs), magnetic cloud-like structures (MCLs), and interplanetary shock waves. Eighty-two MCs and one hundred and twenty-two MCLs were identified by using solar wind and magnetic field data from the WIND mission, and two hundred and sixty-one interplanetary shocks were identified over the period of 1995–2003 in the vicinity of Earth. It is found that MCs are typically more geoeffective than MCLs or interplanetary shocks. The occurrence frequency of MCs is not well correlated with sunspot number. By contrast, both occurrence frequency of MCLs and sudden storm commencements (SSCs) are well correlated with sunspot number.     

Study of the influence of solar variability on a regional (Indian) climate: 1901–2007

We use Indian temperature data of more than 100 years to study the influence of solar activity on climate. We study the Sun–climate relationship by averaging solar and climate data at various time scales; decadal, solar activity and solar magnetic cycles. We also consider the minimum and maximum values of sunspot number (SSN) during each solar cycle. This parameter SSN is correlated better with Indian temperature when these data are averaged over solar magnetic polarity epochs (SSN maximum to maximum). Our results indicate that the solar variability may still be contributing to ongoing climate change and suggest for more investigations.     

太阳黑子自动识别与特征参量自动提取

日面上黑子数目反映了太阳活动水平的高低.黑子形态的复杂性和磁场的非势性与太阳活动爆发密切相关.随着高时空精度的太阳观测数据量的急剧增长，快速准确地自动识别日面上的黑子以及对黑子群特征自动提取已成为太阳活动预报的现实需求.本文针对SDO/HMI的活动区白光数据，利用数学形态法开展黑子自动识别研究，并在黑子识别基础上对黑子群的面积和黑子数进行了计算.通过对利用2011-2017年HMI活动区数据计算得到的黑子群面积和黑子数与NOAA/SWPC发布的活动区相应参量进行比较，发现本文计算结果与SWPC发布数据的变化趋势基本一致，相关性较好.其中黑子群面积的相关系数为0.77，黑子数的相关系数为0.79.研究结果表明，利用本文方法对SDO/HMI数据进行处理，能够得到高时间分辨率的黑子群特征参量，可为太阳活动预报提供及时准确的输入.      

1996-2002年太阳耀斑的统计分析

分析了1996-2002年南北半球的太阳黑子相对数和南北半球太阳X射线耀斑级别(简称Imp)≥M1．0的太阳X射线耀斑的特征和不对称性．分析结果表明，南北半球的太阳耀斑活动的程度交替上升，在2001年7月以前北半球的太阳耀斑活动强于南半球，2001年7月开始耀斑活动逐渐以南半球为主．本文还逐月分析了1996—2001年南北半球的耀斑指数．2000年7月为第23周太阳指数最大的一个月，与第23周太阳黑子相对数最大月均值吻合．     

Solar terrestrial effects of two distinct types

The occurrence frequencies or fluxes of most of the solar phenomena show a 11-year cycle like that of sunspots. However, the average characteristics of these phenomena may not show a 11-year cycle. Among the terrestrial parameters, some related directly to the occurrence frequencies of solar phenomena (for example, ionospheric number densities related to solar EUV fluxes which show 11-year cycle like sunspots) show 11-year cycles, including the double-peak structures near sunspot maxima. Other terrestrial parameters related to average characteristics may not show 11-year sunspot cycles. For example, long-term geomagnetic activity (Ap or Dst indices) is related to the average interplanetary solar wind speed V and the total magnetic field B. The average values of V depend not on the occurrence frequency of ICMEs and/or CIRs as such, but on the relative proportion of slow and high-speed events in them. Hence, V values (and Ap values) in any year could be low, normal or high irrespective of the phase of the 11-year cycle, except that during sunspot minimum, V (and Ap) values are also low. However, 2–3 years after the solar minimum (well before sunspot maximum), V values increase, oscillate near a high level for several years, and may even increase further during the declining phase of sunspot activity, due to increased influence of high-speed CIRs (corotating interplanetary regions). Thus, Ap would have no fixed relationship with sunspot activity. If some terrestrial parameter shows a 11-year cycle, chances are that the solar connection is through the occurrence frequencies (and not average characteristics) of some solar parameter.     

太阳活动对电离层TEC变化影响分析ormalsize

为研究太阳活动对电离层TEC变化的影响,从整体到局部分析了2000—2016年的太阳黑子数、太阳射电流量F_10.7指数日均值与电离层TEC的关系,并重点分析了2017年9月6日太阳爆发X9.3级特大耀斑前后15天太阳活动与电离层TEC变化的相关性.结果表明:由2000—2016年的数据整体看来,太阳黑子数、太阳F_10.7指数、TEC两两之间具有很强的整体相关性,但局部相关性强弱不均;此次耀斑爆发前后太阳黑子数、太阳F_10.7指数和TEC具有很强的正相关特性,太阳活动对TEC的影响时延约为2天;太阳活动对全球电离层TEC的影响不同步,从高纬至低纬约有1天的延迟,且对低纬度的影响远大于中高纬度.太阳活动是影响电离层TEC变化的主要原因,但局部也可能存在其他重要影响因素.      

Even–odd cycle parity in complexity of hemispheric sunspot activity

We have used the Lempel–Ziv measure to describe the complexity in sunspot activity during the solar cycles 18–23. In particular, we examined the time series of daily sunspot numbers in the northern and southern hemispheres in each of the six cycles and calculated the Lempel–Ziv complexity (LZC) value for each time series. Our results indicate that in the even cycles, the LZC values of the sunspot numbers in the two hemispheres are very close to each other, whereas in the odd cycles they differ significantly between the two hemispheres. We also find that within each hemisphere the LZC varies from cycle to cycle. This even–odd cycle parity reflects the variations in inter-hemispheric strengths of the solar magnetic field leading to different temporal distributions of sunspots in the two hemispheres. The degree of complexity may influence the predictability of sunspot activity in the two hemispheres during the various cycles. Although the physical implication of the results is not clear, these results may stimulate new ideas into modeling the complex dynamics of the solar dynamo.     

太阳风速度的周期结构分析

本文应用功率谱估计中的加窗法和最大熵法对第20太阳活动周太阳风速度的周期结构进行了频谱分析;为了克服太阳活动高年瞬变扰动的干扰,本文还用互相关滤波方法与谱分析进行了比较。得到如下结果:除了个别年代外,在太阳活动周的所有相位里,太阳风速度几乎都存在13天和27天两种主要周期变化成份。在一些年里,还有9天的周期成份存在。      

Sunspot activity and cosmic ray modulation at 1 a.u. for 1900–2013

The descent of sunspot cycle 23 to an unprecedented minimum of long duration in 2006–2009 led to a prolonged galactic cosmic ray (GCR) recovery to the highest level observed in the instrumental era for a variety of energetic charged particle species on Earth, over a wide range of rigidities. The remarkable GCR increase measured by several ground-based, balloon-borne, and detectors on a satellite is described and discussed. It is accompanied by a decrease in solar wind velocity and interplanetary magnetic field at 1 a.u., reaching the lowest values since measurements of the solar wind began in October 1963; the solar polar field strength (μT) measured at the Wilcox Solar Observatory (WSO) is also significantly reduced compared to prior cycles since the start of the program in 1976, the polar field in the northern hemisphere reversed in June 2012 and again in February 2014, that in the southern hemisphere reversed in July 2013. If updates of WSO data confirm the second reversal in northern solar hemisphere, it would pose a serious challenge to the Dynamo Theory. The long-term change in solar behavior may have begun in 1992, perhaps earlier. The physical underpinnings of these solar changes need to be understood and their effect on GCR modulation processes clarified. The study discusses the recent phenomena in the context of GCR modulation since 1900. These happenings affected our empirical predictions for the key parameters for the next two sunspot cycles (they may be progressively less active than sunspot cycle 24) but it enhanced support for our prediction that solar activity is descending into a Dalton-like grand minimum in the middle of the twentyfirst century, reducing the frequency of the coronal mass ejections; they determine the space weather affecting the quality of life on Earth, radiation dose for hardware and human activities in space as well as the frequency of large Forbush decreases at 1 a.u.     

Application of support vector machine combined with K-nearest neighbors in solar flare and solar proton events forecasting

The support vector machine (SVM) combined with K-nearest neighbors (KNN), called the SVM-KNN method, is new classing algorithm that take the advantages of the SVM and KNN. This method is applied to the forecasting models for solar flares and proton events. For the solar flare forecasting model, the sunspot area, the sunspot magnetic class, and the McIntosh class of sunspot group and 10 cm solar radio flux are chosen as inputs; for the solar proton event forecasting model, the inputs include the longitude of active regions, the flux of soft X-ray, and those for the solar flare forecasting model. Detailed tests are implemented for both of the proposed forecasting models, in which the SVM-KNN and the SVM methods are compared. The testing results demonstrate that the SVM-KNN method provide a higher forecasting accuracy in contrast to the SVM. It also gives an increased rate of ‘Low’ prediction at the same time. The ‘Low’ prediction means occurrence of solar flares or proton events with predictions of non-occurrence. This method show promise for forecasting models of solar flare and proton events.     

Sunspot cycle 23 descent to an unusual minimum and forecasts for cycle 24 activity

The decay phase of the sunspot cycle 23 exhibited two unusual features. First, it lasted too long. Second, the interplanetary magnetic field intensity at earth orbit reached the lowest value since in situ measurements in space began in October 1963. These physical anomalies significantly altered the early forecasts for the sunspot activity parameters for cycle 24, made by several colleagues. We note that there was a significant change in the solar behavior during cycle 22. We discuss the observed trends and their effect on our empirical solar activity forecast technique, leading to our prediction for cycle 24 parameters; cycle 24 will be only half as active as cycle 23, reaching its peak in May 2013. We speculate on the possible implications of this outcome on future earth climate change and the ensuing socio-economic consequences.     

Solar wind electron density and temperature over solar cycle 23: Thermal noise measurements on Wind

We present the solar wind plasma parameters obtained from the Wind spacecraft during more than nine years, encompassing almost the whole solar cycle 23. Since its launch in November 1994 Wind has frequently observed the in-ecliptic solar wind upstream of the Earth’s bow shock. The WIND/WAVES thermal noise receiver was specially designed to measure the in situ plasma thermal noise spectra, from which the electron density and temperature can be accurately determined. We present and discuss histograms of such measurements performed from 1994 to 2003. Using these large data sets, we study the density and core temperature variations with solar activity cycle and with different regimes of the solar wind. We confirm the anticorrelation of the electron density with the sunspot number, and obtain a positive correlation of the core temperature, with the sunspot number.     

中等磁暴太阳周分布的统计研究

依据实际观测的中等磁暴数据,统计分析了中等磁暴的太阳周分布.分析结果表明,在一个太阳活动周内,每年中等磁暴随时间的变化出现多个峰值,其中,最大峰值均出现在太阳活动周的下降段,即中等磁暴的峰值比太阳黑子数平滑年均值的峰值要滞后,滞后的时间为2～3年.超过70%的中等磁暴出现在太阳活动周的下降段,这表明绝大多数中等磁暴出现在太阳活动周的下降段.通过对中等磁暴平滑月均值与太阳黑子数平滑月均值相位差的计算分析发现,中等磁暴峰值出现的时间比太阳黑子数峰值出现的时间要滞后,不同太阳活动周中等磁暴峰值出现的时间与太阳黑子数峰值时间滞后的程度不同.      

Ionospheric heating due to solar flares as measured by SROSS-C2 satellite

The data on thermal fluctuations of the topside ionosphere have been measured by Retarding Potential Analyser (RPA) payload aboard the SROSS-C2 satellite over the Indian region for half of the solar cycle (1995–2000). The data on solar flare has been obtained from National Geophysical Data Center (NGDC) Boulder, Colorado (USA) and other solar indices (solar radio flux and sunspot number) were download from NGDC website. The ionospheric electron and ion temperatures show a consistent enhancement during the solar flares. The enhancement in the electron temperature is 28–92% and for ion temperature it is 18–39% compared to the normal day’s average temperature. The enhancement of ionospheric temperatures due to solar flares is correlated with the variation of sunspot and solar radio flux (F10.7cm). All the events studied in the present paper fall in the category of subflare with almost same intensity. The ionospheric electron and ion temperatures enhancement have been compared with the IRI model values.     

Specific features of the high-speed plasma stream cycles

The high-speed plasma streams in the solar wind are investigated during the solar cycles nos. 20–22 (1964–1996), separately on the two types of streams according to their solar origin: the HSPS produced by coronal holes (co-rotating) and the flare-generated, in keeping with the classification made in different catalogues. The analysis is performed taking into account the following high-speed stream parameters: the durations (in days), the maximum velocities, the velocity gradients and, the importance of the streams. The time variation of these parameters and the high-speed plasma streams occurrence rate show an 11-year periodicity with some differences between the solar cycles considered. A detailed analysis of the high-speed stream 11-year cycles is made by comparison with the “standard” cycles of the sunspot relative number (Wolf number). The different behaviour of the high-speed stream parameters between even and odd solar cycles could be due to the 22-year solar magnetic cycle. The increased activity of the high-speed plasma streams on the descendant phases of the cycles, regardless of their solar sources, proves the existence of some special local conditions of the solar plasma and the magnetic field on a large scale that allow the ejection of the high energy plasma streams. This fact has led us to the analysis the stream parameters during the different phases of the solar cycles (minimum, ascendant, maximum and, descendant) as well as during the polar magnetic field reversal intervals. The differences between the phases considered are pointed out. The solar cycles 20 and 22 reveal very similar dynamics of the flare-generated and also co-rotating stream parameters during the maximum, descendant and reversal intervals. This fact could be due to their position in a Hale Cycle (the first component of the 22-year solar magnetic cycle). The 21st solar cycle dominance of all co-rotating stream parameters against the 20th and 22nd solar cycle ones, during almost all phases, could be due to the same structure of a Hale Cycle – solar cycle 21 is the second component in a 22-year SC. During the reversal intervals, all high-speed stream parameters have comparable values with the ones of the maximum phases of the cycles even if this interval contains a small part of the descendant branch (solar cycles 20 and 22).