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.     

日冕扰动传播的数值模拟(Ⅲ)太阳风的影响

本文数值研究了二维磁流体动力学平衡基态下开场区日面冷物质径向喷射所引起的日冕动力学响应。结果表明:(1)在高密度环前方有一弱扰动区近似以Alfvén速度向外传播;(2)高密度环前缘移动速度随着径向距离而增加, 其增加值近似为局地太阳风速度;(3)高密度环中等离子体的最大径向速度约在4个太阳半径处趋于局地逃逸速度;(4)对于强开放场, 环形结构在θ方向上没有明显的扩张。这些结果可以更好地解释伴随有日珥的日冕物质抛射事件。     

aa指数与IMF的关系

本文用磁暴期间最大ａａ指数考察了行星际磁场强度Ｂ及其扇形边界对地磁场的影响，根据ａａ与Ｂ的线性关系提出了按Ｂ对磁暴进行分类，并统计了每类磁暴特性与相应的太阳风参数的特性，发现行星际磁场的两类扇形边界扫地球后有不同的地磁效应。     

1998年5月空间天气大事件的地磁场响应

地磁场与1998年5月空间大事件相对应的是5月1日至16日发生的大磁暴（k=8)。磁暴主相开始的几个小时伴随有丰富的Pc型地磁脉动，包括P c2,Pc3,Pc4等。在增暴的恢复相，甚至还有Pc5巨型脉动，在行星标磁场Bz由北向转向南向时，磁暴主相开始；南向分量达到最大值后大约2小时，地磁H分量达到最小值，恢复相开始，并且，这次磁暴与太阳风电场也存在一定的对应关系。     

上游太阳风中高能电子向同步轨道区的传输

通常认为,同步轨道区的电子通量增加是由于磁暴或者上游太阳风高速流的扰动所引起．近来的观测表明,起源于太阳活动的行星际高能电子也是引起同步轨道电子通量增加的重要原因之一．Zhao等在研究2000年7月14日太阳剧烈活动时发现,同步轨道区相对论电子通量巨幅增加时没有观察到上游太阳风高速流的扰动,并且磁暴发生在电子通量事件之后．采用解析磁场模型和实际磁场模型(T96模型)模拟来自太阳的相对论电子在磁尾中的运动特性．计算结果表明,当行星际磁场南向时,进入到磁尾的行星际相对论电子可以从较远的磁尾区域运动到同步轨道区域．这一研究结果从理论上论证了起源于太阳活动的高能电子可以对同步轨道区相对论电子通量的增加产生重要的作用．     

F2层对地磁扰动的响应

利用37个电离层垂直探测站1974-1986年的数据,采用f0F2与地磁ap指数相关分析的方法,首次得到一个太阳活动周期各年东亚-澳大利亚扇区,欧洲-非洲扇区和美洲-东太平洋扇区F2层对地磁扰动响应随地磁纬度的分布.结果指出,地磁高纬和中纬地区为负响应,低纬和赤道地区为正响应,大约在±30°附近换向.最大正响应在磁赤道附近,最大负响应在地磁纬度±50°附近,最大负响应的幅度大于最大正响应的幅度.存在明显的经度差别和南北半球不对称性.     

太阳风中小尺度磁通量管边界重联的统计研究

通过对WIND卫星1995—2005年的数据,利用程序筛选及人工识别两种不同方法确定的小尺度磁通量管进行比较,发现程序筛选法中41%的小尺度磁通量管有边界重联现象,与人工识别法确定的小尺度磁通量管的统计结果接近;通过人工识别和程序筛选两种方法确定的小尺度磁通量管的边界重联特征,包括磁场剪切角、磁场强度以及重联耗散区的持续时间等,也具有相同的统计趋势.结果表明,两种方法确定的小尺度磁通量管在重联特性上没有本质区别,因此采用这两种方法得到的数据作为样本来统计小尺度磁通量管前后边界重联事件.本文共确定了71个重联事件,统计结果显示有50个(70%)重联耗散区磁场的减小超过20%,47个(66%)磁场剪切角大于90°;多数重联事件的磁场剪切角大于90°,表明小尺度磁通量管边界中主要发生的是反平行重联.将小尺度磁通量管的前后边界重联分开进行统计,结果显示其前后边界重联的特征是相似的,与磁云前后边界存在差异的性质不同,这意味着太阳风中的小尺度磁通量管并不具有磁云这种大尺度磁通量管的膨胀特征.     

低轨道中等能量电子对地磁扰动的响应

低轨道高度上能量电子通量变化与地磁扰动程度密切相关.利用我国资源2号(ZY-2)03星空间环境监测分系统在轨工作期间所获得的能量电子探测数据,以及美国NOAA-15,NOAA-16,NOAA-17三颗卫星中等能量电子探测器自1998年以来积累的太阳同步轨道中等能量电子探测数据,结合地磁活动观测数据,对低轨道高度上中等能量电子对地磁扰动的响应特性进行了统计分析.结果表明,该区域的中等能量电子通量在磁暴、磁层亚暴期间有显著增强,增幅大小与地磁活动程度呈正相关关系,强磁暴期间增幅可达一个数量级左右,在响应时间上存在电子通量变化滞后于磁扰的时间特性.     

利用转移熵研究引起磁暴扰动的太阳风参数重要性排序

磁暴是重要空间天气灾害性事件,能够影响卫星的安全在轨运行和地面电网系统等。目前,对于太阳风–磁层相互作用的研究多集中在分析相关系数的线性关系,而基于信息论的转移熵可以提供强大的无模型有向统计量,可用来分析传统相关性分析和模型假设检测不到的非线性关系。本文利用转移熵的方法,研究了磁暴期间的太阳风驱动参数。利用第23和24太阳活动周的小时精度数据进行长时间尺度分析,发现太阳风向地磁的信息传递呈双峰分布,表现出与太阳活动水平的一致性。利用2010－2018年93个地磁暴期间的分钟精度数据进行短时间尺度分析,结果表明：行星际电场（E）和行星际磁场南向分量（$ {B}_{z} $）对地磁指数Sym-H在时间延迟为60 min时信息传递较强,而太阳风速度 $ {v}_{mathrm{s}mathrm{w}} $、温度 $ {T}_{mathrm{s}mathrm{w}} $、数密度$ {D}_{mathrm{s}mathrm{w}} $、磁场B和动压$ {P}_{mathrm{s}mathrm{w}} $对Sym-H指数的信息传递较弱。上述研究结果能够为太阳风–磁层相互作用的建模提供参数选择及确定预测范围的依据。     

Geosynchronous magnetic field response to the large and fast solar wind dynamic pressure change

We present a comparison of large and sharp solar wind dynamic pressure changes, observed by several spacecraft, with fast disturbances in the magnetospheric magnetic field measured by the GOES-8, 9 and 10 geosynchronous satellites. Almost 400 solar wind pressure changes in the period 1996–2003 were selected for this study. Using the large statistics we confirmed that increases (decreases) in the dynamic pressure always results in increases (decreases) in the magnitude of geosynchronous B_z component. The amplitude of the geosynchronous B_z response strongly depends on the location of observer relative to the noon meridian, from the value of solar wind pressure before the disturbance arriving and firstly – from the amplitude of the pressure change.     

Long-term changes in indices of geomagnetic activity at the auroral station Sodankylä

Here we compare the traditional analog measure of geomagnetic activity, Ak, with the more recent digital indices of IHV and Ah based on hourly mean data, and their derivatives at the auroral station Sodankylä. By this selection of indices we study the effects of (i) analog vs. digital technique, and (ii) full local-time vs. local night-time coverage on quantifying local geomagnetic activity. We find that all other indices are stronger than Ak during the low-activity cycles 15–16 suggesting an excess of very low scalings in Ak at this time. The full-day indices consistently depict stronger correlation with the interplanetary magnetic field strength, while the night-time indices have higher correlation with solar wind speed. The Ak index correlates better with the digital indices of full-day coverage than with any night-time index. However, Ak depicts somewhat higher activity levels than the digital full-day indices in the declining phase of the solar cycle, indicating that, due to their different sampling rates, the latter indices are less sensitive to high-frequency variations driven by the Alfvén waves in high-speed streams. On the other hand, the night-time indices have an even stronger response to solar wind speed than Ak. The results strongly indicate that at auroral latitudes, geomagnetic indices with different local time coverage reflect different current systems, which, by an appropriate choice of indices, allows studying the century-scale dynamics of these currents separately.     

The characteristics of sharp (small-scale) boundaries of solar wind plasma and magnetic field structures

We investigate properties of large (>20%) and sharp (<10 min) solar wind ion flux changes using INTERBALL-1 and WIND plasma and magnetic field measurements from 1996 to 1999. These ion flux changes are the boundaries of small-scale and middle-scale solar wind structures. We describe the behavior of the solar wind velocity, temperature and interplanetary magnetic field (IMF) during these sudden flux changes. Many of the largest ion flux changes occur during periods when the solar wind velocity is nearly constant, so these are mainly plasma density changes. The IMF magnitude and direction changes at these events can be either large or small. For about 55% of the ion flux changes, the sum of the thermal and magnetic pressure are in balance across the boundary. In many of the other cases, the thermal pressure change is significantly more than the magnetic pressure change. We also attempted to classify the types of discontinuities observed.     

Variations of the magnetosheath ion flux and geomagnetic activity

The magnetosheath plays a dominant role in the Sun–Earth connection because the magnetosheath field and plasma actually interact with the magnetosphere. The interactions change the magnetospheric magnetic field from its nominal value through a long chain of different processes. The change is usually described by geomagnetic indices and thus it can be expected that these indices would reflect changes in the magnetosheath. The present paper analyzes the relation between geomagnetic activity characterized by changes of the K_p, D_ST and AE indices and ion flux measured in the night-side magnetosheath. The results suggest a weak dependence of the D_ST index on the ion flux in the inner magnetosheath that is connected with a magnetopause displacement. On the other hand, fluctuations of the ion flux in the analyzed frequency range do not correlate with any of the indices.     

1998年10月18---19日磁暴主相的行星际源分析

采用高时间分辨率的地磁指数SYM-H, 同时考虑日地连线引力平衡点(L1点)太阳风地磁效应的滞后性, 精确分析了1998年10月18---19日大磁暴主相的行星际源. 分析结果表明, 磁暴主相的行星际源仅为行星际激波和行星际日冕物质抛射之间的太阳风(Sheath), 磁云对磁暴主相没有贡献. 这个磁暴事例的研究表明, 行星际磁场南向分量与太阳风动压的乘积是影响磁暴主相发展的关键参数.     

The thermospheric composition different responses to geomagnetic storm in the winter and summer hemisphere measured by “SZ” Atmospheric Composition Detectors

Three “SZ” Atmospheric Composition Detectors (ACDs) on board spacecraft “SZ-2”, “SZ-3” and “SZ-4” were launched on 10th January 2001, 26th March 2002 and 31st December 2002 separately. A large quantity of thermospheric composition data at the orbital altitude ranging from 330 to 362 km were collected from the in-situ measurement of ACDs. The spacecrafts’ lifetime was just in the second peak period of the 23rd solar cycle which includes two peaks and the solar activity value F_10.7 was from 89 to 228. During this period, several intense geomagnetic disturbances happened.     

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.