基于机器学习相似度算法的Kp指数预报

基于机器学习中的相似度算法,建立了在历史太阳风数据中寻找与当前太阳风特征相近事例的推荐模型,用来预报地磁Kp指数.使用1998-2019年间随机选择的120个太阳风事例作为测试数据集,该模型能够推荐得到历史上与输入太阳风造成相似地磁影响的太阳风事例,最优事例的Kp指数与实际值的均方根误差为0.79,相关系数为0.93....     

ULF wave index as magnetospheric and space-weather parameters

Waves in the Ultra Low Frequency (ULF) band owe their existence to solar wind turbulence and transport momentum and energy from the solar wind to the magnetosphere and farther down. Therefore an index based on ULF wave power could better characterize solar wind–magnetosphere interaction than K_P, Dst, AE, etc. indices which described mainly quasi-study state condition of the system. We have shown that the ULF wave index accurately characterize relativistic electron dynamics in the magnetosphere as these waves are closely associated with circulation, diffusion and energization of relativistic electrons in the magnetosphere. High speed solar wind streams also act as a significant driver of activity in the Earth’s magnetosphere co-rotating interaction region and are responsible for geomagnetic activities. In the present paper, we have analyzed various cases related with very weak (quiet) days, weak days, storm days and eclipse events and discussed the utility of the ULF wave index to explain the magnetospheric dynamics and associated properties. We have tried to explain that the ULF wave index can equally be useful as a space weather parameter like the other indices.     

太阳风扰动对极光电急流和环电流指数的影响

利用WIND卫星的太阳风观测数据和地磁活动指数, 研究了太阳风扰动对环电流SYM-H指数, 西向极光电急流AL指数和东向极光电急流AU指数的影响. 结果表明, 太阳风动压增长和减少能够同步或延迟引起地磁活动指数的强烈扰动, 其包括环电流指数的上升, 西向极光电急流指数的下降和东向极光电急流指数的上升. 太阳风动压的突然剧烈增加还能够触发超级亚暴和大磁暴. 太阳风动压脉冲引起的地磁效应具有复杂的表现形式, 这说明太阳风动压脉冲的地磁效应不仅与太阳风动压脉冲大小和持续时间有关, 还与磁层本身所处的状态有关. 时间尺度较长, 消耗能量较大的磁暴只有大的持续时间较长的太阳风动压脉冲才能激发.      

Geomagnetic storm effects on the earth''s ozone layer

The study of the response of the terrestrial environment to the different forms of solar activity is a relevant task. Geomagnetic perturbations arise from the solar wind/magnetospheric coupling and major magnetic storms are caused by intense, long duration Southward interplanetary magnetic fields. This paper addresses reader's attention on possible effects induced by geomagnetic storms on the Earth's ozone layer by reporting a series of experimental results related to the topic. Difficulties connected with a right assessment of such kind of effects are described.     

冕洞特征参数与地磁暴强度及发生时间统计

地磁暴是空间天气预报的重要对象.在太阳活动周下降年和低年，冕洞发出的高速流经过三天左右行星际传输到达地球并引发的地磁暴占主导地位.目前地磁暴的预报通常依赖于1AU处卫星就位监测的太阳风参数，预报提前量只有1h左右.为了增加地磁暴预报提前量，需要从高速流和地磁暴的源头即太阳出发，建立冕洞特征参数与地磁暴的定量关系.分析了2010年5月到2016年12月的152个冕洞-地磁暴事件，利用SDO/AIA太阳极紫外图像提取了两类冕洞特征参数，分析了其与地磁暴期间ap，Dst和AE三种地磁指数的统计关系，给出冕洞特征参数与地磁暴强度以及发生时间的统计特征，为基于冕洞成像观测提前1～3天预报地磁暴提供了依据.      

太阳风和地球磁层相互作用的两种可能类型

本文对太阳活动20周不同活动期间的太阳风参数与地磁活动性指数分别进行了相关分析,并进一步对太阳活动极大和极小年分别对B_z和太阳风参数V、T、N的时均值日方差作了分析比较。结果指出,除目前普遍认为的IMF与地磁场重联导致的磁扰外,还有一类与B_z无关,而是由高温、高速、热不均匀太阳风等离子体导致的地磁扰动类型。      

地球磁场对太阳风扰动响应的研究

分别对行星际激波、太阳风动压增大事件和减小事件的地球磁场响应进行了比较. 分析结果表明, 同步轨道磁场对太阳风扰动在向阳面产生较强的正响应, 在背阳面 响应较弱且有时会出现负响应, 地磁指数SYM-H对太阳风扰动的响应为正响应. 同时还得出, 向阳侧同步轨道磁场响应幅度d Bz与地磁指数响应幅度d SYM-H、上下游动压均方差均具有较好的相关性. 地磁指数响应幅度与同步轨道磁场响应幅度相关关系在激波和动压增大事件中具有一致性, 动压减小事件出 现明显差异, 这说明激波和动压增大事件在影响地球磁场方面具有某种共性.      

Evolution of Dst index,cosmic rays and global temperature during solar cycles 20–23

We have studied conditions in interplanetary space, which can have an influence on galactic cosmic ray (CR) and climate change. In this connection the solar wind and interplanetary magnetic field parameters and cosmic ray variations have been compared with geomagnetic activity represented by the equatorial Dst index from the beginning 1965 to the end of 2012. Dst index is commonly used as the solar wind–magnetosphere–ionosphere interaction characteristic. The important drivers in interplanetary medium which have effect on cosmic rays as CMEs (coronal mass ejections) and CIRs (corotating interaction regions) undergo very strong changes during their propagation to the Earth. Because of this CMEs, coronal holes and the solar spot numbers (SSN) do not adequately reflect peculiarities concerned with the solar wind arrival to 1 AU. Therefore, the geomagnetic indices have some inestimable advantage as continuous series other the irregular solar wind measurements. We have compared the yearly average variations of Dst index and the solar wind parameters with cosmic ray data from Moscow, Climax, and Haleakala neutron monitors during the solar cycles 20–23. The descending phases of these solar cycles (CSs) had the long-lasting solar wind high speed streams occurred frequently and were the primary contributors to the recurrent Dst variations. They also had effects on cosmic rays variations. We show that long-term Dst variations in these solar cycles were correlated with the cosmic ray count rate and can be used for study of CR variations. Global temperature variations in connection with evolution of Dst index and CR variations is discussed.     

Input Parameters for Models of Energetic Electrons Fluxes at the Geostationary Orbit

The results of cross-correlation analysis between electrons fluxes (with energies of > 0.6MeV, > 2.0 MeV and > 4.0MeV), geomagnetic indices and solar wind parameters are shown in the paper. It is determined that the electron fluxes are controlled not only by the geomagnetic indices, but also by the solar wind parameters, and the solar wind velocity demonstrates the best relation with the electron fluxes. Numerical value of the relation efficiency of external parameters with the highly energetic electrons fluxes shows a periodicity. It is presented here the preliminary results of daily averaged electrons fluxes forecast for a day ahead on the basis of the model of neuron networks.     

Advances in space research nonlinear dependence of Dst and AE indices on the electric field of magnetic clouds

Using the Dst and AE geomagnetic index values and parameters of interplanetary magnetic field and solar wind we have examined the geoeffectiveness of transient ejections in the solar wind, namely, magnetic clouds and high-speed streams. It is found that for magnetic clouds the dependences of indices on the solar wind electric field are nonlinear of different kind. In contrast to magnetic clouds, the dependence of Dst and AE geomagnetic index values on the solar wind electric field agrees closely with the linear one for high-speed streams. We suggest approximating formulas to describe dependences obtained taking into account the relation of the electric field transpolar potential to the electric field and dynamic pressure of the solar wind. We suppose that the interplanetary magnetic field fluctuations also contribute to these dependences.     

Geoeffectiveness of interplanetary shocks controlled by impact angles: A review

The high variability of the Sun’s magnetic field is responsible for the generation of perturbations that propagate throughout the heliosphere. Such disturbances often drive interplanetary shocks in front of their leading regions. Strong shocks transfer momentum and energy into the solar wind ahead of them which in turn enhance the solar wind interaction with magnetic fields in its way. Shocks then eventually strike the Earth’s magnetosphere and trigger a myriad of geomagnetic effects observed not only by spacecraft in space, but also by magnetometers on the ground. Recently, it has been revealed that shocks can show different geoeffectiveness depending closely on the angle of impact. Generally, frontal shocks are more geoeffective than inclined shocks, even if the former are comparatively weaker than the latter. This review is focused on results obtained from modeling and experimental efforts in the last 15?years. Some theoretical and observational background are also provided.     

Chaos and multifractals in the solar wind

By using the false-nearest-neighbours method, we have argued that the deterministic component of solar wind plasma dynamics should be low-dimensional. In fact, the results we have obtained using the method of topological embedding indicate that the behaviour of the solar wind can be approximately described by a low-dimensional chaotic attractor in the inertial manifold, which is a subspace of system phase space. We have also shown that the multifractal spectrum of the solar wind attractor is consistent with that for the multifractal measure of the self-similar generalized weighted Cantor set with two different scaling parameters and one probability measure parameter responsible for nonuniform compression in phase space and multifractality. The values of the parameters fitted also demonstrate that the complex solar wind system could only be weakly non-conservative (small dissipation) and quantify nonlinear dynamics; some parts of the attractor in phase space are visited much more frequently than other parts. In addition, to quantify the multifractality of space plasma intermittent turbulence, we consider that generalized Cantor set also in the context of scaling properties of solar wind turbulence. We investigate the resulting multifractal spectrum of a one-dimensional phenomenological model of turbulence cascade depending on its parameters, especially for asymmetric scaling. In particular, we have shown that intermittent pulses are stronger for the cascade model with two different scaling parameters. Even thought solar wind turbulence appears to be rather space filling, a better agreement with the data is obtained, especially for the negative index of generalized dimensions. Therefore we argue that there is a need to use a two-scale asymmetric cascade model. We hope that this generalized multifractal model will be a useful tool for analysis of intermittent turbulence in space plasmas. We thus believe that fractal analysis of chaotic systems could lead us to a deeper understanding of their nature, and maybe even to predict their seemingly unpredictable behaviour.     

Prompt effects of solar wind variations on the inner magnetosphere and midlatitude ionosphere

It is well known that the solar wind can significantly affect high-latitude ionospheric dynamics. However, the effects of the solar wind on the middle- and low-latitude ionosphere are much less studied. In this paper, we report observations that large perturbations in the middle- and low-latitude ionosphere are well correlated with solar wind variations. In one event, a significant (20–30%) decrease of the midlatitude ionospheric electron density over a large latitudinal range was related to a sudden drop in the solar wind pressure and a northward turning of the interplanetary magnetic field, and the density decrease became larger at lower latitudes. In another event, periodic perturbations in the dayside equatorial ionospheric E × B drift and electrojet were closely associated with variations in the interplanetary electric field. Since the solar wind is always changing with time, it can be a very important and common source of ionospheric perturbations at middle- and low-latitudes. The relationship between solar wind variations and significant ionospheric perturbations has important applications in space weather.     

2008—2009年电离层对重现型地磁活动的响应

利用2008—2009年的GPS TEC数据,分析了电离层对冕洞引起的重现型地磁活动的响应. 结果表明,在太阳活动低年,电离层TEC表现出与地磁 ap指数（采用全球3h等效幅度指数ap来表征）和太阳风速度相似的9天和13.5天短周期变化,表明TEC的这种短周期特性主要与重现型地磁活动相关. 地磁纬度和地方时分析表明,夜间高纬地区正负相扰动明显,中低纬地区则以正相扰动为主,较大的TEC变幅主要发生在南北半球高纬地区,夜间南半球高纬地区TEC变化相对ap指数变化有相位延迟. 白天中低纬地区正负相扰动明显,TEC短周期变化与ap指数变化相位基本一致. 2008年TEC的9天和13.5天周期变化幅度大于2009年.      

Contribution of geometry of interaction between interplanetary and terrestrial magnetic fields into global magnetospheric state and geomagnetic activity

The paper presents results of our study of dependence of geomagnetic activity from geoeffective parameters taking into account mutual orientation of the interplanetary magnetic field, electric field of the solar wind and geomagnetic moment. We attract a reconnection model elaborated by us made allowance for changes of geometry of the solar wind–magnetosphere interaction during annual and diurnal motions of the Earth. We take as our data base the interplanetary magnetic field and solar wind velocity measured at 1 a.u. at ecliptic plane for the period of 1963–2005 and K_p, D_st, a_m indices. Taken as a whole a geoeffective parameter suggested by us explains 95% of observed variations of the indices. Changes of the geometric factor determined by mutual orientation of the solar wind electric field and geomagnetic moment explain larger than 75% of observed statistical variations of D_st and a_m indices. Based on our results we suggest a new explanation of semi-annual and UT variation of geomagnetic activity.     

Large geomagnetic storms of extreme solar event periods in solar cycle 23

During extreme solar events such as big flares or/and energetic coronal mass ejections (CMEs) high energy particles are accelerated by the shocks formed in front of fast interplanetary coronal mass ejections (ICMEs). The ICMEs (and their sheaths) also give rise to large geomagnetic storms which have significant effects on the Earth’s environment and human life. Around 14 solar cosmic ray ground level enhancement (GLE) events in solar cycle 23 we examined the cosmic ray variation, solar wind speed, ions density, interplanetary magnetic field, and geomagnetic disturbance storm time index (D_st). We found that all but one of GLEs are always followed by a geomagnetic storm with D_st  −50 nT within 1–5 days later. Most(10/14) geomagnetic storms have D_st index  −100  nT therefore generally belong to strong geomagnetic storms. This suggests that GLE event prediction of geomagnetic storms is 93% for moderate storms and 71% for large storms when geomagnetic storms preceded by GLEs. All D_st depressions are associated with cosmic ray decreases which occur nearly simultaneously with geomagnetic storms. We also investigated the interplanetary plasma features. Most geomagnetic storm correspond significant periods of southward B_z and in close to 80% of the cases that the B_z was first northward then turning southward after storm sudden commencement (SSC). Plasma flow speed, ion number density and interplanetary plasma temperature near 1 AU also have a peak at interplanetary shock arrival. Solar cause and energetic particle signatures of large geomagnetic storms and a possible prediction scheme are discussed.     

Statistical characteristics of low latitude Pc4s: Influence of solar wind and IMF parameters

Pc4 signatures for the year 2013, extracted from geomagnetic north–south and east–west components of induction coil magnetometer (LEMI 30) from low latitude station Desalpar (DSP), operated by Institute of Seismological Research (ISR), India have been investigated vis-à-vis the prevalent interplanetary parameters (IMF) as well as the geomagnetic activity indices. A clear dominance of Pc4-5 (467 events) over Pc3 (17 events) is observed. Local time variation of Pc4 shows a peak in the noon sector in both X and Y components. Our investigations show that the dominant peak frequency is 10 mHz at low latitude region. Correlations with solar wind and IMF parameters illustrate highest occurrence of Pc4 for a solar wind speed of 300–400 km/s and average IMF B field of 3–6 nT. The amplitude of Pc4s at DSP shows an increase with increasing solar wind speed, plasma density, solar wind dynamic pressure and average B field which is also reflected in the trend of frequency variation of these pulsations. We report that IMF clock angle at low latitude does not have influence on Pc4 occurrence. Based on the characteristics of these events, detected in latitudinally distributed stations from low and mid-latitudes from northern and southern hemisphere, we infer that modes were compressional, which could be driven by K-H instability or solar wind dynamic pressure, as compressional modes can propagate to low latitude with little attenuation.     

Strong perturbations on the Sun and in the heliosphere leading to large geomagnetic storms: Similar and individual characteristics

We briefly present the selected results obtained up to now by the Russian scientific groups regarding powerful solar ejections as main causes of large geomagnetic storms in the near-Earth space. Strongest perturbations on the Sun and in the near-Earth space responsible for large geomagnetic storms were well registered and analyzed during the 23rd solar cycle. Open issues and perspectives are discussed.     

冕洞特征参数与重现型地磁暴关系的统计研究

在提取冕洞特征参数的基础上,利用1996年到2005年8月近十年来对地磁扰动有影响的356个冕洞事例,定量分析了冕洞特征参数(包括冕洞的面积比、经纬度跨度等)与冕洞高速流特征、重现型地磁扰动特征(包括扰动大小和持续时间等)之间的相关性,研究发现,从引起地磁扰动的冕洞在整个太阳活动周的分布来看,在地磁扰动峰年中冕洞影响同样具有重要的贡献;冕洞高速流太阳风速度与地磁扰动强度之间存在较强的相关性,而高速流中太阳风速度与冕洞面积比关系不大,与冕洞亮度存在一定相关性;冕洞的经度跨度与地磁扰动持续时间存在很强的正相关性.