Variation in the Flaring Potential of Different Sunspot Groups During Different Phases of Solar Cycles 23 and 24

In this present study,we have analyzed different types of X-ray solar flares(C,M,and X classes)coming out from different classes of sunspot groups(SSGs).The data which we have taken under this study cover the duration of 24 yr from 1996 to 2019.During this,we observed a total of 15015 flares(8417 in SC-23 and 6598 in SC-24)emitted from a total of 33780 active regions(21746 in SC-23 and 12034 in SC-24)with sunspot only.We defined the flaring potential or flare-production potential as the ratio of the total number of flares produced from a particular type of SSG to the total number of the same-class SSGs observed on the solar surface.Here we studied yearly changes in the flaring potential of different McIntosh class groups of sunspots in different phases of SC-23 and 24.In addition,we investigated yearly variations in the potential of producing flares by different SSGs(A,B,C,D,E,F,and H)during different phases(ascending,maximum,descending,and minimum)of SC-23 and 24.These are our findings:(1)D,E,and F SSGs have the potential of producing flares≥8 times greater than A,B,C and H SSGs;(2)The larger and more complex D,E,and F SSGs produced nearly 80%of flares in SC-23 and 24;(3)The A,B,C and H SSGs,which are smaller and simpler,produced only 20%of flares in SC-23 and 24;(4)The biggest and most complex SSGs of F-class have flaring potential 1.996 and 3.443 per SSG in SC-23 and 24,respectively.(5)The potential for producing flares in each SSG is higher in SC-24 than in SC-23,although SC-24 is a weaker cycle than SC-23.(6)The alterations in the number of flares(C+M+X)show different time profiles than the alterations in sunspot numbers during SC-23 and 24,with several peaks.(7)The SSGs of C,D,E,and H-class have the highest flaring potential in the descending phase of both SC-23 and 24.(8)F-class SSGs have the highest flaring potential in the descending phase of SC-23 but also in the maximum phase of SC-24.

Dreicer Electric Field Definition and Runaway Electrons in Solar Flares

We analyze electron acceleration by a large-scale electric field E in a collisional hydrogen plasma under the solar flare coronal conditions based on approaches proposed by Dreicer and Spitzer for the dynamic friction force of electrons.The Dreicer electric field EDr is determined as a critical electric field at which the entire electron population runs away.Two regimes of strong(E≲E_(Dr))and weak(E≪E_(Dr))electric field are discussed.It is shown that the commonly used formal definition of the Dreicer field leads to an overestimation of its value by about five times.The critical velocity at which the electrons of the"tail"of the Maxwell distribution become runaway under the action of the sub-Dreiser electric fields turns out to be underestimated by√3 times in some works because the Coulomb collisions between runaway and thermal electrons are not taken into account.The electron acceleration by sub-Dreicer electric fields generated in the solar corona faces difficulties.

恒星超级耀斑的研究进展

太阳耀斑是太阳系内最剧烈能量释放现象之一,其在数十分钟之内可以释放高达1025 J的能量。随着观测技术的发展,在恒星上也观测到类似的耀发事件,其典型强度是太阳耀斑的10∼10^(4)倍,被称为超级耀斑。研究恒星超级耀斑及其爆发机制,不仅在理解恒星内部结构、演化与磁场活动性质等方面起到重要的作用,而且对探究太阳系外行星宜居性和系外生命具有重要意义。首先扼要介绍了太阳耀斑及其相关磁活动现象、恒星磁场以及恒星超级耀斑;然后从恒星超级耀斑的筛选、能量计算、恒星黑子、耀斑参数与恒星参数的统计关系等方面叙述了对恒星超级耀斑的探测手段以及研究成果,并与太阳耀斑理论与相关物理过程进行对比,以探讨两者之间的相似性以及与现有理论的联系;最后进行了总结,并对将来可能开展的相关工作进行展望。

Main Sequence Star Super-flare Frequency based on Entire Kepler Data

We wrote and used an automated flare detection Python script to search for super-flares on main sequence stars of types A,F,G,K and M in Kepler's long-cadence data from Q0 to Q17.We studied the statistical properties of the occurrence rate of super-flares.For the G-type data set,we compared our results with the previous results of Okamoto et al.by splitting the data set into four rotational bands.We found similar power-law indices for the flare frequency distribution.Hence,we show that inclusion of a high-pass filter,sample biases,gyrochronology and completeness of flare detection is of no significance,as our results are similar to those of Okamoto et al.We estimated that a super-flare on G-type dwarfs with energy of 10^(35) erg occurs on a star once every 4360 yr.We found 4637 super-flares on 1896 G-type dwarfs.Moreover,we identified 321,1125,4538 and 5445 super-flares on 136,522,770 and 312 dwarfs of types A,F,K and M,respectively.We ascertained that the occurrence rate(dN/dE)of super-flares versus flare energy,E,shows a power-law distribution with dN/dE∝E^(-α),whereα■2.0 to 2.1 for the spectral types from F-type to M-type stars.In contrast,the obtainedα■1.3 for A-type stars suggests that the flare conditions differ from those of the other spectral-type stars.We note an increase in flare incidence rate in F-type to M-type stars and a decrease in A-type to F-type stars.

Construction and Validation of a Geometry-based Mathematical Model for the Hard X-Ray Imager

Quantitative and analytical analysis of the modulation process of the collimator is a great challenge,and is also of great value to the design and development of Fourier transform imaging telescopes.The Hard X-ray Imager(HXI),as one of the three payloads onboard the Advanced Space-based Solar Observatory(ASO-S) mission,adopts modulating Fourier-Transformation imaging technique and will be used to explore the mechanism of energy release and transmission in solar flare activities.As an important step to reconstruct the images of solar flares,accurate modulation functions of HXI are needed.In this paper,a mathematical model is developed to analyze the modulation function under a simplified condition first.Then its behavior under six degrees of freedom is calculated after adding the rotation matrix and translation change to the model.In addition,unparalleled light and extended sources are also considered so that our model can be used to analyze the X-ray beam experiment.Next,applied to the practical HXI conditions,the model has been confirmed not only by Geant4 simulations but also by some verification experiments.Furthermore,how this model helps to improve the image reconstruction process after the launch of ASO-S is also presented.

Flare Forecast Model Based on DS-SMOTE and SVM with Optimized Regular Term

The research of flare forecast based on the machine learning algorithm is an important content of space science.In order to improve the reliability of the data-driven model and weaken the impact of imbalanced data set on its forecast performance,we proposes a resampling method suitable for flare forecasting and a Particle Swarm Optimization(PSO)-based Support Vector Machine(SVM)regular term optimization method.Considering the problem of intra-class imbalance and inter-class imbalance in flare samples,we adopt the density clustering method combined with the Synthetic Minority Over-sampling Technique(SMOTE)oversampling method,and performs the interpolation operation based on Euclidean distance on the basis of analyzing the clustering space in the minority class.At the same time,for the problem that the objective function used for strong classification in SVM cannot adapt to the sample noise,In this research,on the basis of adding regularization parameters,the PSO algorithm is used to optimize the hyperparameters,which can maximize the performance of the classifier.Finally,through a comprehensive comparison test,it is proved that the method designed can be well applied to the flare forecast problem,and the effectiveness of the method is proved.

LyαEmission Enhancement Associated with Soft X-Ray Microflares

Lyα(Lyα,1216 A)is the strongest emission line in the solar ultraviolet spectrum.In the present work,we obtained a Lyαenhancement catalog covering flares larger than B1 class from the GOES/EUVS data during 2010-2016.We focused on the 242 B-class events which are less investigated,however,show non-negligible Lyαemission enhancement.We found that on average the Lyαpeak of B-class flares is 0.85%stronger than the background.For the flare energetics,it is found that the weaker the soft X-ray(SXR)flare,the larger the ratio of the radiated energy in Lyαto SXR.Using the RHESSI data and multi-wavelength observations taken by SDO-AIA,we diagnose the thermal and non-thermal properties of several flares.Three case studies show that the coincidence of the Lyαpeak with the SXR time-derivative peak is not a sufficient condition of the nonthermal property of a Lyαmicroflare.The Lyαenhancement in the microflares may be caused by the nonthermal electron beams or/and thermal conduction.However for typeⅢevents,we found that the delay of the Lyαpeak with respect to the SXR peak can be attributed to either the Lyαemission from a filament erupted or the cooling of the thermal plasma in flare loops.Furthermore,interestingly the Lyαemission from filaments can not only occur in the decay phase of the flare,but also in the preflare phase.In this case,the Lyαemission was originated from an erupted filament which probably initiated the flare.

Change Ratios of Magnetic Helicity and Magnetic Free Energy During Major Solar Flares

Magnetic helicity is an important concept in solar physics,with a number of theoretical statements pointing out the important role of magnetic helicity in solar flares and coronal mass ejections(CMEs).Here we construct a sample of 47 solar flares,which contains 18 no-CME-associated confined flares and 29 CME-associated eruptive flares.We calculate the change ratios of magnetic helicity and magnetic free energy before and after these 47 flares.Our calculations show that the change ratios of magnetic helicity and magnetic free energy show distinct different distributions in confined flares and eruptive flares.The median value of the change ratios of magnetic helicity in confined flares is-0.8%,while this number is-14.5%for eruptive flares.For the magnetic free energy,the median value of the change ratios is-4.3%for confined flares,whereas this number is-14.6%for eruptive flares.This statistical result,using observational data,is well consistent with the theoretical understandings that magnetic helicity is approximately conserved in the magnetic reconnection,as shown by confined flares,and the CMEs take away magnetic helicity from the corona,as shown by eruptive flares.

Martian Thermosphere Response to Solar Flares:MAVEN NGIMS Observations

The solar flare is a sudden eruptive solar phenomenon with significant enhancements in solar X-ray and Extreme Ultraviolet radiations,resulting in large amounts of energy being injected into the planetary atmosphere.Case studies have been extensively presented to analyze the effect of extremely large flares on the Martian upper atmosphere,but the general features of the Martian thermospheric response to flares are still poorly understood.In this work,we select 12 intense solar flares that occurred between 2015 and 2017 and investigate the densities and compositional variations of the dayside Martian thermosphere to these flares with the aid of the measurements made by the Mars Atmosphere and Volatile EvolutioN.The statistical studies indicate that the responses of the Martian thermosphere to flares are complicated that both the class of the flare and the wavelength of the enhanced radiation may have prominent influences on the thermal expansion of the atmosphere and the atmospheric photochemical reactions.

Research Progress on Solar Flare Forecast Methods Based on Data-driven Models

Eruption of solar flares is a complex nonlinear process,and the rays and high-energy particles generated by such an eruption are detrimental to the reliability of space-based or ground-based systems.So far,there are not reliable physical models to accurately account for the flare outburst mechanism,but a lot of data-driven models have been built to study a solar flare and forecast it.In the paper,the status of solar-flare forecasting is reviewed,with emphasis on the machine learning methods and data-processing techniques used in the models.At first,the essential forecast factors strongly relevant to solar flare outbursts,such as classification information of the sunspots and evolution pattern of the magnetic field,are reviewed and analyzed.Subsequently,methods of resampling for data preprocessing are introduced to solve the problems of class imbalance in the solar flare samples.Afterwards,typical model structures adopted for flare forecasting are reviewed from the aspects of the single and fusion models,and the forecast performances of the different models are analyzed.Finally,we herein summarize the current research on solar flare forecasting and outline its development trends.

基于对流参数的洋口港地区雷暴预报方法研究

文章分析了洋口港地区2001—2009年4—9月1645个样本22种对流参数与雷暴事件的相关性以及这些参数的统计特征。结果表明,各对流参数月际分布差异较大,各参数与雷暴事件相关系数也不同。因而选择沙氏指数SI、全总指数TT、杰弗逊指数JI、抬升凝结高度温度tcl_t、上下层温差dt_58、大气可降水量p_w、风暴强度指数SSI等7个对于雷暴活动具有较好相关性的因子,并考虑到4—9月月际分布差异,使用不同月份p_w、SI、TT、JI的不同阈值作为排空因子,不同月份SSI、tcl_t、dt_58的不同阈值作为预报因子,使用二级逻辑回归法建立排空方程和预报方程,同时对所建立各月预报方程进行了检验和拟合结果分析,并对2010年4—9月样本进行试报,预报效果较好。

利用GPS监测电离层总电子含量的季节性变化

利用Georgiadiou电离层模型计算了GPS系统硬件延迟,从而由双频伪距观测值获取绝对电离层总电子含量值。利用北京IGS站的GPS观测数据分别计算了2000年和2004年各个不同月份的总电子含量值,对两年各月份的总电子含量进行多项式拟合,发现总电子含量的季节性变化趋势一致。

2001年4月2日太阳耀斑及其太阳质子事件的观测结果研究

20 0 1年 4月 2日 ,太阳爆发了一个近年来X射线通量最大的一次耀斑并伴有质子事件 ,利用“资源一号”卫星星内粒子探测器和神舟二号飞船X射线探测器的观测资料 ,对这一事件的高能粒子响应进行了特例研究 .“资源一号”卫星运行于太阳同步轨道 ,高度约 80 0km ,和宁静时期的统计结果对比 ,这次耀斑后 ,星内粒子探测器在地球极盖区 (地球开磁场区 )观测到耀斑粒子的出现 ,这是宁静时期没有的 ;神舟二号飞船轨道高度 4 0 0km ,倾角为 4 2° ,X射线探测器在 4 2°中高纬地区也观测到高能电子通量比宁静时明显的增加 ,这表明 ,太阳耀斑引起的近地空间辐射环境的变化遍及纬度约 4 0°以上的区域 ,甚至在 4 0°N附近 4 0 0km左右的高度上仍然有响应 .但是 ,中高纬度、极光带和极盖区的粒子来源 ,加速机制和响应方式却不一定相同 ,需要分别讨论 .资料分析和对比还表明 ,质子事件的强度并不一定和耀斑的X射线通量成正比 ,因此 。

青海高原雷暴气候特征及其变化分析

利用青海高原41个气象台站1961-2007年雷暴资料,分析了雷暴活动的时空分布特征,采用趋势系数、倾向率、绝对变率和滑动t检验等统计方法分析了雷暴变化趋势和振荡周期。结果表明:近47年青海高原雷暴总体呈减少趋势,但各区变化特征不一致,雷暴多的地区减少趋势越明显,雷暴最少的柴达木盆地变化不明显,甚至略有增加;雷暴初日表现为显著的推迟趋势,雷暴终日呈显著的提前趋势,雷暴期在缩短;青海南部高原雷暴出现最早,结束最晚,柴达木盆地出现最晚,结束最早;年雷暴日数在2000年发生明显突变,周期分析发现存在准5年周期振荡;20世纪80年代中期以后,雷暴天气引起的雷击、暴雨灾害在逐年增多。

太阳质子事件警报

采用人工神经网络预报方法，利用太阳耀斑的日面位置、X射线辐射的峰值流量及其上升时间、2695MHz和8800MHz微波辐射的半积分流量等5个物理参量，提出了一个新的太阳质子事件警报方案，预报太阳质子事件的发生及其流量和时间．该方案在本文检验中达到93．75％的预报准确率．

太阳耀斑的GPS监测方法及实例分析

利用GPS伪距与载波相位联合数据处理的方法 ,分析了 2 0 0 0年 7月 1 4日太阳耀斑爆发期间 ,武汉、北京、乌鲁木齐GPS观测数据得到的电离层TEC 。

南京地区雷暴活动强度潜势预报

利用江苏省2008、2009和2010年6—8月闪电定位资料对雷暴活动的强度进行了分级,并使用同一时段的探空资料计算了47个代表南京地区环境层结特征的对流参数,利用其与雷暴活动强度的相关性选取预报因子。在此基础上,采用Bayes分类法和Logistic回归分析法,结合逐步选择法进一步筛选预报因子,分别建立了两种雷暴强度的预报模型。通过检验独立样本对比分析两种模型的预报效果,结果表明,Logistic回归分析法的Hedike技巧评分为0.396,并能识别出30%的强雷暴,而Bayes分类法的Hedike技巧评分为0.370,只能识别出5%的强雷暴。Logistic回归分析法对雷暴强度的潜势预报具有较好的指示意义。进一步分析进入预报模型的9个对流参数,表明雷暴活动越强时,低层空气越暖湿,中层空气越干冷,高低层的风切变越大。

耀斑的短期生物效应

为研究太阳耀斑的短期生物效应 ,统计分析了 1 985— 1 995年中 1 6万婴儿出生日与光学耀斑的关系 .结果表明 ,婴儿出生数的变化与耀斑辐射的能量 ,以及能量到达地球的时间有关 .太阳活动较平稳年白天爆发的各级耀斑的当天都对应着一个平均出生数高峰 ,而且耀斑的亮度和面积越大 ,对应的出生峰值越大 .2B耀斑当天平均出生数超过前后 2 1d总均值的 1 3.6 % ,具有p<0 .0 0 1的统计高度显著性水平 .这些出生高峰与耀斑的电磁和高能辐射有关 .2B、2N和 1B三类耀斑后的第 2— 4d还有一个出生峰 ,它们与耀斑引发的地球物理变化的时间符合 .

1991年3月22日耀斑激波的传播特性

采用ＭＨＤ数值方法研究了１９９１年３月２２日２２：４７ＵＴ日面大耀斑引起的行星际激波传播的几何特性，以及初始驱动时间对传播的影响。得出：１．该激波在黄道面投影是非对称的，最快处偏离耀斑法线向东；２．激波面偏离球面，但随着远离太阳这种偏离减小；３．总能相同时，驱动时间短的激波较强，速度较快；能量变化范围相同时，不同初速比不同驱动时间对激波传播速度影响更大。

利用MF雷达对耀斑期间电离层D区电子密度的观测研究

利用MF雷达观测资料对X级别耀斑爆发期间在66—80 km高度之间的电子密度进行了研究,观测到了耀斑爆发期间电子密度的突然增加,在较低高度上的电子密度的时间变化趋势与耀斑的软X射线辐射通量相关.电子密度的变化强度依赖于具体的耀斑参数,有些耀斑引起的电子密度增加高达400 cm-3,有些仅为100 cm-3左右.但耀斑期间在这一高度区间增加的总电子含量增量仅占耀斑辐射引起的整个电离层总电子含量增量的千分之一左右.最后,利用恢复阶段电子密度的时间变化过程估算了1997年11月4日耀斑期间部分高度上的有效复合系数.