行星际激波传播至1AU的渡越时间预测

考虑了激波爆发源角宽度、能量、驱动时间、激波速度及其与背景太阳风之间的相互作用,利用流体力学扰动方程建立起一个激波扰动传播模型,用于研究激波从太阳传播到地球轨道附近(1 AU处)所需要的时间(渡越时间)问题.为印证扰动传播模型的适用性,利用1979-1989年间的27个激波事件,以及1997年2月到2000年1月间的68个激波事件,对激波到达地球轨道附近的渡越时间进行了预测,并将结果与STOA和ISPM预报模型结果进行了比较.实验表明,该模型在所有95个事件中,渡越时间相对误差小于10%的事件数占总事件数的25.26%;相对误差小于20%的占总事件数的50.53%;相对误差小于30%的占总事件的65.26%.     

行星际激波对地球磁层的压缩效应分析

2004 年11月9日WIND飞船探测到一个典型的行星际激波. 激波前行星际磁场为持续约50 min的弱南向磁场, 越过激波面, 磁场发生北向偏转且太阳风动压脉冲增强. 在此强动压脉冲增强结构作用下, 磁层被压缩至一个很小的区域. 激波作用于磁层时引起地球同步轨道 各区域高能粒子通量的响应, 但是不同磁地方时的高能粒子通量的响应不同, 表现出双模式扰动, 即在晨昏两侧各能段的电子和质子通量显著增强, 在子夜侧发生类似于亚暴的无色散粒子注入现象. 扰动从向阳面传输到背阳面, 向阳面粒子通量最先增强, 随后背阳面靠近晨昏两侧, 粒子通量开始增强, 最后子夜侧粒子通量表现出无色散高能粒子注入的特点. 另外, 在靠近正午侧, 质子通量先于电子通量发生响应, 在子夜侧电子通量则先于质子通量发生响应. 利用位于向阳面正午两侧的GOES-10 和 GOES-12卫星观测数据发现, 激波作用于磁层时靠近晨侧的磁场变化表现出简单压缩效应, 而靠近昏侧的磁场变化则显然不同, Bx分量减弱, Bz分量几乎减为零, 而By分量则显著增强. 此外, 位于近地磁尾低纬尾瓣区的TC-1卫星观测到激波触发的尾瓣SI现象.     

夜侧极区电离层对流对行星际激波的响应

利用超级双子极光雷达网（Super Dual Aurora Radar Network,SuperDARN）高频雷达、北半球IMAGE地磁台链以及南极中山站的极光观测数据,研究电离层对流对2012年7月14日一个行星际激波扰动事件的响应.在18：10UT行星际激波到达地球并与磁层相互作用触发地磁急始和磁层亚暴,SuperDARN雷达观测到北半球夜侧极区电离层对流显著增强,观测视野覆盖黄河站的Hankasalmi雷达观测到从激波到达地球至18：33UT,电离层F层出现剧烈扰动,雷达回波数明显增多,并出现局部对流速度反转现象.18：33UT之后,观测到F层出现三块速度高达600m·s^-1的逆阳运动不规则体.而与Hankasalmi雷达地磁共轭的南半球Kerguelen雷达探测到的回波主要来自E层,回波数量几乎无变化,但是Kerguelen雷达观测视野内的中山站全天空光学成像仪观测到极光活动显著增强.南北半球夜侧电离层观测结果的差异,主要是由于它们分别处于极夜和极昼.     

行星际激波导致的磁尾等离子片中ULF波动事件

磁层中的超低频(ULF)波动在太阳风和磁层之间的能量输运过程中具有重要作用.ULF波动主要发生在内磁层,且内磁层中ULF波动影响粒子的加速及沉降,而在夜侧磁层尤其是磁尾等离子片中观测到的ULF波动比较少.基于中国自主磁层探测卫星TC-1的观测数据,发现了两例行星际激波导致的磁尾中心等离子片中ULF波动事件,并发现这两例...     

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.     

Propagation of normal and faster CMEs in the interplanetary medium

We have analyzed 101 Coronal Mass Ejection (CME) events and their associated interplanetary CMEs (ICMEs) and interplanetary (IP) shocks observed during the period 1997–2005 from the list given by Mujiber Rahman et al. (2012). The aim of the present work is to correlate the interplanetary parameters such as, the speeds of IP shocks and ICMEs, CME transit time and their relation with CME parameters near the Sun. Mainly, a group of 10 faster CME events (V_INT > 2200 km/s) are compared with a list of 91 normal events of Manoharan et al. (2004). From the distribution diagrams of CME, ICME and IP shock speeds, we note that a large number of events tends to narrow towards the ambient (i.e., background) solar wind speed (∼500 km/s) in agreement with the literature. Also, we found that the IP shock speed and the average ICME speed measured at 1 AU are well correlated. In addition, the IP shock speed is found to be slightly higher than the ICME speed. While the normal events show CME travel time in the range of ∼40–80 h with a mean value of 65 h, the faster events have lower transit time with a mean value of 40 h. The effect of solar wind drag is studied using the correlation of CME acceleration with interplanetary (IP) acceleration and with other parameters of ICMEs. While the mean acceleration values of normal and faster CMEs in the LASCO FOV are 1 m/s², 18 m/s², they are −1.5 m/s² and −14 m/s² in the interplanetary medium, respectively. The relation between CME speed and IP acceleration for normal and faster events are found to agree with that of  and  except slight deviations for the faster events. It is also seen that the faster events with less travel time face higher negative acceleration (>−10 m/s²) in the interplanetary medium up to 1 AU.     

How do interplanetary shock impact angles control the size of the geoeffective magnetosphere?

In this paper, we investigate temporal and spatial magnetosphere response to the impact of interplanetary (IP) shocks with different inclinations and speeds on the Earth’s magnetosphere. A data set with more than 500 IP shocks is used to identify positive sudden impulse (SI⁺) events as expressed by the SuperMAG partial ring current index. The SI⁺ rise time (RT), defined as the time interval between compression onset and maximum SI⁺ signature, is obtained for each event. We use RT and a model suggested by Takeuchi et al. (2002) to calculate the geoeffective magnetospheric distance (GMD) in the shock propagation direction as a function of shock impact angle and speed for each event. GMD is a generalization of the geoeffective magnetosphere length (GML) suggested by Takeuchi et al. (2002), defined from the subsolar point along the X line toward the tail. We estimate statistical GMD and GML values which are then reported for the first time. We also show that, similarly to well-known results for RT, the highest correlation coefficient for the GMD and impact angle is found for shocks with high speeds and small impact angles, and the faster and more frontal the shock, the smaller the GMD. This result indicates that the magnetospheric response depends heavily on shock impact angle. With these results, we argue that the prediction and forecasting of space weather events, such as those caused by coronal mass ejections, will not be accurately accomplished if the disturbances’ angles of impact are not considered as an important parameter within model and observation scheme capabilities.     

Numeric simulations of in situ observations of interacting ejecta near 1 AU

We use a simple numerical model (González-Esparza, J.A., Santillán, A., Ferrer, J. A numerical study of the interaction between two ejecta in the interplanetary medium: one and two dimensional hydrodynamic simulations, Ann. Geophys. 22, 3741–3749, 2004) to study the evolution of three events in the solar wind reported by Wang et al. (Wang, Y.M., Ye, P.Z., Wang, S. Multiple magnetic clouds: several examples during March–April 2001. J. Geophys. Res. 108, 1370, 2003, doi:10.1029/2003JA009850), where two interacting ejecta detected in situ by ACE near 1 AU were related to CMEs observed previously by SOHO-LASCO. The study is based on a 1-D hydrodynamic model using the ZEUS code (Stone, J.M., Norman, M. ZEUS 2-D: A radiation magnetohydrodynamics code for astrophysical flows in two dimensions, I, the hydrodynamics algorithms and tests, Astrophys. J. 80, 753, 1992). Although this model cannot address either the magnetic field dynamics or the complex geometrical effects intrinsic in the three-dimensional nature of the phenomena, it illuminates the transferring of momentum and evolution of interacting large-scale solar wind disturbances in those cases where there is no merging (magnetic reconnection) between the two ejecta. This model can reproduce, in some cases, characteristics of the events such as transit times and flow signatures as inferred from the two-point measurements from spacecraft.     

Forward and reverse CIR shocks at 4–5 AU: Ulysses

In this article, we study fast shocks at CIR boundaries during an extended interval of 15 consecutive major high speed solar wind streams in 1992–1993. Ulysses was 4–5 AU from the sun. The Abraham-Schrauner shock normal method and the Rankine-Hugoniot relations were used to determine fast shock directions and speeds. Out of 33 potential CIR shocks, 14 were determined to be fast forward shocks (FSs) and 14 were fast reverse shocks (RSs). Of the remaining 5 events, 2 were forward waves and 3 were reverse waves. CIR edges at latitudes below ∼30^o were, for the most part, bounded by fast magnetosonic shocks. The forward shocks were generally quasi-perpendicular (average θ_nBo = 67^o). The reverse shocks were more oblique (average θ_nBo = 52^o), but they extended to all angles. Both FSs and RSs had magnetosonic Mach numbers ranging from 1 to 5 or 6. The average Mach numbers were 2.4 and 2.6 for FSs and RSs, respectively. The shock Mach numbers were noted to generally decrease with increasing latitude. The non-shock events or waves were noted to occur preferentially at high (∼−30° to −35°) heliolatitudes where stream-stream interactions were presumably weaker. These results are consistent with expectations, indicating the general accuracy of the Abraham-Schrauner technique.     

黄道面内行星际激波相互碰撞作用过程研究—能量效应

本文用两维半MHD数值模型,数值模拟研究了两邻近扰动源所产生的激波在行星际空间黄道面内不同能量时的相互碰撞过程。在内边界(18R_s)两扰动中心的间距取为36°。结果表明:两弱激波(速度在500km/s左右以下)不会产生汇合,而是各自独立地传播;两中等强度激波(速度在1000km/s左右)将发生汇合,但在IAU尚可分辨;两强激波(速度在2000km/s以上)则在1AU以内已发生汇合,汇合后形成一个新激波,其磁场结构与单激波明显不同。激波能量越大,两激波汇合的越快。     

黄道面内行星际激波相互碰撞作用过程研究—间距效应

本文用两维半MHD数值模型,模拟研究了不同间距的两扰动源所产生的激波在行星际空间黄道面内的相互碰撞过程。在内边界(18R_s),两扰动中心的间距取为24°、36°、48°、54°、72°、120°,模拟了两激波速度均为1000km/s和2000km/s两种情形。结果表明:1.速度为1000km/s的两中等激波,相距24°时,在1AU以内强烈相互作用而汇合成一新激波;相距36°时,在1AU附近发生汇合,但尚可分辨;相距48°时,在1AU以内有相互作用,但可近似认为是独立传播的;相距72°时,将独立向前传播。2.速眨为2000km/s的两强激波,相距≤48°时,将强烈汇合成一新激波;相距54°时,在1AU附近产生汇合,但尚可分辨;相距72°时,相互作用不足以汇合成新的激波;相距120°时,其传播相互独立地进行。并给出了上述情形下两激波汇合的时间和位置,详细比较了汇合激波与相同能量的单激波的等离子体特性。