太阳风引起的地磁扰动的参数辨识

作为太阳风引起的地磁扰动的系统辨识一文的姊妹篇,本文利用参数系统辨识方法,对太阳风-磁层耦合系统做了进一步的探讨.根据地磁扰动机制的理论研究,地磁扰动被认为是太阳风能量耦合进入磁层以及由此引起的一系列磁层内能量的输运和耗散的结果.在此基础上,对太阳风-磁层系统的非线性情况进行了讨论,建立了D_st指数与太阳风参量的非线性函数关系,给出了由此得到的地磁扰动计算结果.同时还利用1967年2月3-12日和1980年12月16-23日的两次事件,对已得到的函数关系进行了验证和讨论.验证结果不仅对模型的合理性、普适性做了很好的说明,也表明这种非线性函数关系作为定量的地磁预报模型,具有一定的可信度和实用性.     

基于Weimer模型的高纬地磁扰动预测

地磁扰动是空间天气中的重要现象,对地基技术系统具有重要的影响.准确预报地磁扰动可以有效避免重大灾害发生.本文基于Weimer电势和磁势模型发展了高纬地区地磁扰动的模拟方法,并与地面台站观测数据进行了比较.地表磁场扰动主要受电离层电流系统的影响,利用Weimer模式计算出电离层等效电流分布后,基于毕奥-萨伐尔定律推导了地磁扰动三分量与电流的关系,最终计算出地磁扰动量.模型的输入参数为太阳风速度、太阳风密度、行星际磁场和磁偶极倾角.模型计算结果与不同纬度和经度的地磁台站观测结果对比表明本文的计算方法能有效地模拟地磁暴期间地磁扰动特征.本文结果对今后发展高纬地区地磁场预报模型奠定了重要基础.     

太阳风引起的地磁扰动的辨识建模

本文作为地磁扰动系统辨识研究系列的第３篇文章，首先对太阳风－磁层能量耦合进行分析，在此基础上总结和建立一个含有待定参数的物理模型．然后利用参数辨识方法，具体地确定这些参数和函数，从而得到一个完整而确定的数学物理模型，并对这一模型的实用性和可信度进行检验．另外，还选择１９７２年８月事件进行了一次预报实验，即根据太阳耀斑的观测，利用ＨＡ方法和文中得到的模型，分两步实现对地磁扰动的预报．     

基于复杂度理论的地磁变化场时间序列特征分析

复杂度理论为研究地磁变化场提供了新思路和新途径.地磁变化场从物理起源上可以看作是一种复杂系统,因此,本文从军事工程应用需求出发,基于复杂度理论,提出运用样本熵、多尺度熵及滑动窗样本熵方法对不同磁扰程度下的地磁变化场时间序列进行复杂度特征分析,结果表明：（1）样本熵和多尺度熵能够很好地表征地磁扰动强度及演化特征,启发我们可设计一种新的“熵指数”来衡量地磁扰动大小;（2）滑动窗样本熵能够准确定位地磁扰动时间段,对于磁暴识别与预测、空间灾害性天气预警等有一定的参考价值;（3）Mackey-Glass时滞混沌方程随时间的演化呈现出与地磁场日变曲线非常相似的形态,因此,地磁变化场或许可用时滞混沌方程来表示,对于我们更好地认识地磁变化场物理机理、建模预测与地磁寻的等军事工程应用都有一定的意义.     

磁层亚暴与磁层暴（Ⅱ）:太阳风参数对Dst的影响机制研究

为了研究地磁活动指数D_st受太阳风参数影响,包括行星际磁场（IMF）南向分量B_st、太阳风速度V_?和太阳风-磁层发电机电动势U调制的机制,应用太阳风-磁层-电离层输入-输出[I（t）-O（t）]电网络模型,对磁层亚暴与磁层暴过程中,B_z（t）-D_st、V-a（t）-D_st和U（t）-D_st的激励-响应特性进行模拟。研究表明,B_z是形成亚暴与磁层暴的前提条件,V_st是形成亚暴与磁层暴的充分条件,二者统一于电动势U_st研究结果与观测结果一致。     

关于日地关系主要元素与各种指数——综述及展望

本文着眼于日地空间物理之间的因果联系,从源头即太阳发生扰动时输出的各种形式的能量如电磁辐射、粒子辐射和电磁场等到行星际空间的表现和演化.到地球空间环境包括：磁层-电离层-中高层大气等对太阳事件的响应变化,论述了日地关系中的主要物理、化学过程及其之间的相互关系.同时,对日地系统发生变化时的各种表征参量,包括地磁指数、太阳辐射指数和太阳风-磁层耦合函数等,以及各参量对整体的日地空间环境预报中可能的应用前景进行了综述和展望.     

三十年来我国地磁和高空物理学的进展

本文对三十年来我国地磁和高空物理学的进展,作了较系统的评述,分下列14个方面:（1）地磁台的建设,（2）地磁测量和中国地磁图,（3）地磁短期变化和磁暴预报,（4）岩石磁性、古地磁和考古地磁,（5）大地电磁勘探和有关的工作,（6）磁法勘探及推断方面的发展,（7）地磁地电仪器的研制,（8）震磁关系的探索和理论研究,（9）日地关系若干统计分析,（10）高层大气结构和臭氧层测定,（11）关于电离层的探测和分析研究,（12）磁层结构和扰动,（13）宇宙线强度变化的测定和研究,（14）简短的回顾和展望。     

第23太阳活动周期太阳风参数及地磁指数的统计分析

日冕物质抛射(Coronal Mass Ejection,简称CME)和共转相互作用区(Corotating Interaction Region,简称CIR)是造成日地空间行星际扰动和地磁扰动的两个主要原因,提供了地球磁暴的主要驱动力,进而显著影响地球空间环境.为深入研究太阳风活动及受其主导影响的地磁活动的时间分布特征,本文对大量太阳风参数及地磁活动指数的数据进行了详细分析.首先,采用由NASA OMNIWeb提供的太阳风参数及地磁活动指数的公开数据,通过自主编写matlab程序对第23太阳活动周期(1996-01-01—2008-12-31)的数据包括行星际磁场Bz分量、太阳风速度、太阳风质子密度、太阳风动压等重要太阳风参数及Dst指数、AE指数、Kp指数等主要的地磁指数进行统计分析,建立了包括269个CME事件和456个CIR事件列表的数据库.采用事例分析法和时间序列叠加法分别对两类太阳活动的四个重要太阳风参数(IMF Bz、太阳风速度、太阳风质子密度、太阳风动压)和三个主要地磁指数(Dst、AE、Kp)进行统计分析,并研究了其统计特征.其次,根据Dst指数最小值确定了第23太阳活动周期内的355个孤立地磁暴事件,并以Dst指数最小值为标准将这些磁暴进一步分类为145个弱磁暴、123个中等磁暴、70个强磁暴、12个剧烈磁暴和5个巨大磁暴.最后,采用时间序列叠加法对不同强度磁暴的太阳风参数和地磁指数进行统计分析.统计分析表明,对于CME事件,Nsw/Pdyn(Nsw表示太阳风质子密度,Pdyn表示太阳风动压)线性拟合斜率一般为正;对于CIR事件,Nsw/Pdyn线性拟合斜率一般为负,这可作为辨别CME和CIR事件的一种有效方法.从平均意义上讲,相较于CIR事件,CME事件有更大的南向IMF Bz分量、太阳风动压Pdyn、AE指数、Kp指数以及更小的Dstmin.一般情况下,CME事件有更大的可能性驱动极强地磁暴.总体而言,对于不同强度的地磁暴,Dst指数的变化呈现出一定的相似性,但随着地磁暴强度的增强,Dst指数衰减的速度变快.CME和CIR事件以及其各自驱动的地磁暴事件有着很多不同,因此,需要将CME事件驱动的磁暴及CIR事件驱动的磁暴分开研究.建立CME、CIR事件及地磁暴的数据库以及获取的统计分析结果,将为深入研究地球磁层等离子体片、辐射带及环电流对太阳活动的响应特征提供有利的帮助.     

太阳风特性的地磁响应

本文利用逐步回归方法分析了地磁指数 AE、Dst、Ap 与多种太阳风参数的关系。找出了影响地磁场变化的主要太阳风特征参数为磁场分量 Bz、与动能有关的量 NV~2、电场-VBz及磁声速 Cas。不同的地磁参数对太阳风特征参数的响应也不同。     

行星际背景太阳风的三维MHD数值模拟

近地空间的太阳风参数预报具有重要的科学研究意义和实际应用价值,三维磁流体力学（MHD）数值模拟是太阳风参数预报的重要手段.本文建立了一套基于经验模型的三维MHD数值模型.模型的内边界设置在0.1天文单位（AU）处,在六片网格系统下利用TVD Lax-Friedrich格式求解理想MHD方程组,采用扩散法消除磁场的散度.模型以GONG的观测磁图作为输入数据,利用经验模型并结合卫星观测特征确定内边界条件.边界条件中保留了6个可调参数,以便适当调整参数使其方便适合模拟不同太阳活动期的太阳风.利用该模型分别模拟了2007年和2016年的背景太阳风,得到了太阳风速度、密度、温度和磁场强度,这些参数与ACE/WIND卫星观测符合较好.     

Studying correlations between the coronal hole area,solar wind velocity,and local magnetic indices in the Canadian region during the decline phase of cycle 23

Geomagnetic disturbances in the Canadian region are compared with their solar and heliospheric sources during the decline phase of solar activity, when recurrent solar wind streams from low-latitude coronal holes were clearly defined. A linear correlation analysis has been performed using the following data: the daily and hourly indices of geomagnetic activity, solar wind velocity, and coronal hole area. The obtained correlation coefficients were rather low between the coronal hole areas and geomagnetic activity (0.17–0.48), intermediate between the coronal hole areas and the solar wind velocity (0.40–0.65), and rather high between the solar wind velocity and geomagnetic activity (0.50–0.70). It has been indicated that the correlation coefficient values can be considerably increased (by tens of percent in the first case and about twice in the second case) if variations in the studied parameters related to changes in the ionosphere (different illumination during a year) and variations in the heliolatitudinal shift of the coordinate system between the Earth, the Sun, and a spacecraft are more accurately taken into account.     

Forbush effects with a sudden and gradual onset

For a comprehensive study of the Forbush effects and their relation to solar and geomagnetic activity, a database of transient phenomena in cosmic rays and the interplanetary medium has been created, which is continuously updated with data on new events. Based on these data, we study the dependence of the Forbush effects on various internal and external parameters, as well as select different groups of events. In this paper, we consider recurrent (caused by high-speed solar wind streams from coronal holes) and sporadic (associated with coronal mass ejections) events. We investigate groups of events with a sudden and gradual onset. We show that the resulting dependencies of the Forbush effects (on the parameters of interplanetary disturbances, geomagnetic activity indices, etc.) are substantially different for the above-mentioned groups. Most likely, these differences are caused by different sources of solar wind disturbances.     

Magnetospheric disturbances excited by solar wind density enhancements on April 11, 1997

Disturbances in the solar wind density, geomagnetic field, and magnetospheric plasma density and fluxes are analyzed. The disturbances have the same sign and are close to each other in time. They accompany the process of amplitude modulation of Pc1 geomagnetic pulsations during the recovery phase of the moderate magnetic storm of April 10–11, 1997. The magnetospheric disturbances were recorded by ground-based observatories and on spacecraft in all local time sectors with insignificant time delays. It is concluded that in this case variations in the geomagnetic field and magnetospheric plasma density are primary, whereas the amplitude modulation of Pc1, 2 is a secondary manifestation of fast magnetosonic (FMS) waves that are generated during the interaction between the magnetosphere and solar wind density irregularities.     

Response of the geomagnetic activity to solar wind turbulence during solar cycle 23

The solar wind–magnetosphere coupled system is characterized by dynamical processes. Recent works have shown that nonlinear couplings and turbulence might play a key role in the study of solar wind–magnetosphere interaction processes.Within this framework, this study presents a statistical analysis aimed to investigate the relationship between solar wind MHD turbulence and geomagnetic activity at high and low latitudes as measured by the AE and SYM-H indices, respectively. This analysis has been performed for different phases of solar cycle 23. The state of turbulence was characterized by means of 2-D histograms of the normalized cross-helicity and the normalized residual energy. The geomagnetic response was then studied in relation to those histograms.The results found clearly show that, from a statistical point of view, solar cycle 23 is somewhat peculiar. Indeed, good Alfvénic correlations are found unexpectedly even during solar activity maximum. This fact has implications on the geomagnetic response as well since a statistical relationship is found between Alfvénic fluctuations and auroral activity. Conversely, solar wind turbulence does not seem to play a relevant role in the geomagnetic response at low latitudes.     

Low-latitude variations in the geomagnetic field caused by solar wind disturbances

In view of the actual question regarding the effect of a solar-wind pressure jump on disturbances in the Earth’s magnetosphere, events with high velocity and density gradients are of special interest. In this work, we consider the response of the current at the dayside magnetopause to these events and the corresponding strengthening of the geomagnetic field in the low-latitude magnetosphere. A transient process is studied that accompanies reconfiguration of the magnetosphere under the effect of disturbances of solar wind parameters. An analytical equation is received for estimation of an increase in the northern component of low-latitude magnetic field of the magnetosphere in a transient current system (transient ring current) versus initial values of the solar-wind velocity and density and their disturbances.     

Variations of Geomagnetic Cosmic Ray Thresholds and Their Latitudinal Behavior in the Period of Solar Disturbance in September 2005

The period of interplanetary, geomagnetic and solar disturbances of September 7–15, 2005, is characterized by two sharp increases of solar wind velocity to 1000 km/s and great Dst variation of the geomagnetic field (~140 nT). The time variations of theoretical and experimental geomagnetic thresholds observed during this strong geomagnetic storm, their connection with solar wind parameters and the Dst index, and the features of latitudinal behavior of geomagnetic thresholds at particular times of the storm were studied. The theoretical geomagnetic thresholds were calculated with cosmic ray particle tracing in the magnetic field of the disturbed magnetosphere described by Ts01 model. The experimental geomagnetic thresholds were specified by spectrographic global survey according to the data of cosmic ray registration by the global station network.     

Dynamical Climatology of the Upper Mesosphere, Lower Thermosphere and Ionosphere

The main features of upper atmosphere dynamics as an important part of upper atmosphere climatology are presented. The dynamics of the mesosphere and lower thermosphere (MLT) are of special interest. The results are based on the long series of investigations in East Siberia and data from a world-wide network of observatories. We present the regional climatic norms for the prevailing wind and semi-diurnal tide and the main features of the quasi-periodic structure of the wind field. The non-zonality of MLT dynamics is demonstrated as well as regional differences in the response of the wind field to stratospheric disturbances, solar activity variations and geomagnetic storms.