【作者】 张莹；

【导师】 冯学尚； 魏奉思；

【作者基本信息】 中国科学院研究生院（空间科学与应用研究中心） ， 空间物理， 2009， 博士

【摘要】 太阳瞬变活动如太阳耀斑、日冕物质抛射(CME)和射电爆发等,以及冕洞太阳风高速流是空间天气的主要驱动源,是造成行星际扰动及相应地磁扰动的主要原因,对日地空间环境具有举足轻重的影响。本文借助数值模拟和统计分析相结合的方法,对太阳活动、行星际扰动和相应地磁扰动的相关性及相关的预报方法进行了研究。利用Hakamada-Akasofu-Fry(HAF)太阳风模型,通过比较有无爆发事件发生时的模拟结果,首次区分了第23太阳周(1996～2005)的三种行星际结构:“纯”-共转相互作用区(CIR),CIR与行星际日冕物质抛射(ICME)的相互作用结构和“纯”-ICME。在此基础上对CIR的重现型地磁活动;CIR与激波、磁暴的关系进行了统计性分析,其结果如下:(1)在第23太阳活动周共识别了157个CIR事件,大部分事件发生在下降相。(2)引入相邻卡林顿周的Kp指数的相关系数( CCKCCR )来反映地磁活动的重现性程度。CCKCCR的最大值出现在太阳活动下降相,表明重现型地磁活动在这个时期占主导地位。通过分析冕洞的纬度和CCKCCR的关系,可以看出CIR在重现型地磁活动的重要作用。(3)在1AU处,41%的CIR可以形成激波,且多为前向激波,其原因可能是:相对于背景太阳风,前向激波是远离太阳,向西且向赤道传播的,而后向激波是靠近太阳,向东且向极区传播的,因而在1AU处黄道面附近的Wind,ACE卫星观测到更多的是前向激波。(4)CIR引发的磁暴与激波没有必然联系,仅有44%与激波相伴随。(5)当Dst指数大于-100 nT时,CIR引起的磁暴的Dst指数与行星际磁场Bz,晨昏电场Ey,和太阳风-磁能耦合函数(ε)具有较好的线性相关关系。(6)由于地球和太阳相对位置的变化,CIR的地磁活动具有明显的季节效应,在二分点(春分和秋分)附近最强。这些统计结果,可以为CIR地球物理效应的中长期预报提供重要参考。建立了一种预报激波到达时间的数据库新方法。基于HAFv.1模式,利用大量虚拟事件建立一个激波渡越时间数据库,该数据库包括:虚拟事件的源位置,初始激波速度,发生年份以及其对应的渡越时间。只要输入太阳观测事件的源位置,初始激波速度和与第23太阳周相应的发生年份,就可以在数据库中迅速查找到该事件所对应的激波到达时间。对于1997年2月到2002年8月间的130个历史激波事件的预报试验表明数据库方法的预报能力并不亚于STOA、ISPM、HAFv.2模型,从而显示了该模型在空间天气实时预报中所具有的潜力。另外,由于太阳活动的周期性,我们选取了23个其他太阳活动周的事件,尝试用该数据库进行预报,也得到了较好的预报结果。这表明,该数据库方法可能也适用于其他太阳周。然而,该数据库方法也有它的不足之处,如没有考虑源表面磁场的短期变化,致使大尺度日球电流片位形以及背景太阳风结构等都有所偏差,使得该方法的预报结果存在一定误差。另外,为了简单起见,该数据库方法向其它太阳周的拓展也没有得到较好的太阳活动周的相位对应。这些因素将会在未来的工作中考虑。目前的工作旨在提供一种可以迅速预报激波到达时间的新方法。给出预报行星际激波到达时间的两种一维数值模型:一种是基于一维流体方程,采用Roe格式建立起来的激波扰动的传播模型(称之为1D-HD模型);另一种是采用时空守恒元和解元( CE/SE )方法建立起来的一维磁流体(MHD )激波传播模型(称之为1D-MHD(CE/SE)模型)。选取了一定的激波样本事件,对激波到达地球轨道附近的传播时间进行了预测,并将预报结果与STOA,ISPM,HAFv.2以及SPM模型所得结果进行了比较。结果表明,这两种模型的预报精度与其它模型相比基本相当。表明这两种模型在空间天气的激波到达时间的预报方面有潜在的应用价值。这两个模型虽然是简单的一维数值模型,但却可以达到迅速预报激波到达时间的目的,而且可以通过进一步的改进,期望可以对激波能否到达1AU及地球轨道给出判断。更多还原

【Abstract】 Solar transient activities, such as solar ?ares, coronal mass ejections (CMEs),radio bursts, and fast solar wind from coronal hole are important drivers of spaceweather as they can induce interplanetary disturbances and trigger geomagneticstorms. They play important roles in leading to adverse solar-terrestrial environ-ment. In this paper, based on numerical simulation and statistical analysis, thecorrelations between the solar transients, interplanetary disturbances and corre-sponding geomagnetic disturbances together with the related prediction methodsare investigated.Three kinds of interplanetary structures:“pure”corotating interaction re-gions (CIR), interaction of CIR with interplanetary coronal mass ejection (ICME),and“pure”ICME caused by transient events, are identified for the first time byusing the Hakamada-Akasofu-Fry (HAF) model. We investigated CIRs’recur-rent geomagnetic activity and the relations among CIRs, shocks and geomagneticstorms in the heliosphere (< 1AU) during solar cycle 23 (1996～2005). The mainresults are: (1) There are 157“pure”CIRs in the 23rd solar cycle and most ofCIRs occur in the declining phase. (2) CCKCCR is calculated to represent thelevel of recurrent geomagnetic disturbances. The maximum CCKCCR appearsduring the descending phase near solar minimum so that recurrent geomagneticactivity is dominant during this period. The relation between the latitude ofcoronal hole and CCKCCR shows that CIRs play important roles in recurrentgeomagnetic activity. (3) 41% of CIRs are associated with interplanetary shocksat 1AU and most of shocks are forward shocks. This is probably the reason whyWind and ACE near the ecliptic plane are expected to see more forward shocks’propagating antisunward, westward, and equatorward than reverse shocks’prop-agating sunward, eastward, and poleward if both types of shocks form near oneAU. (4) CIR-related shock is not a necessary condition for generating a mag-netic storm, only 44% CIR-related storms were related to CIR-related shocks,but most CIR-related shocks are related to storms. (5) The Dst index that cor- responds to CIR-related storms has a better linear relationship with IMF Bz,Ey, and the coupling function (ε) when the Dst indices are higher than -100 nT.(6) The geoe?ectiveness of CIRs appears clearly to have seasonal e?ects due tothe changing relative orientation of the Earth and the Sun. The overall geomag-netic disturbance levels are higher at autumn equinox for antisunward directionof interplanetary magnetic field( IMF) and spring equinox for sunward direc-tion. These statistical results will be useful for the long-term prediction in thegeoe?ectiveness of CIRs.A practical database method for predicting the interplanetary shock arrivaltime at L1 point is presented. A shock transit time database based on HAFv.1(version 1 of the Hakamada-Akasofu-Fry model) is established. The databaseorganized on a multidimensional grid of source location, initial coronal shockspeed, and the year of occurrence of the hypothetical solar event. The arrivaltime at L1 for any given solar event occurring in the 23rd solar cycle can bepredicted by looking up in the grid of the database according to source location,the initial coronal shock speed, and the year of occurrence in cycle 23. Theprediction test of the 130 observed solar events during the period from February1997 to August 2002 shows that its success rate could be practically equivalentto those by the shock time of arrival (STOA) model, the interplanetary shockpropagation model (ISPM), and the HAFv.2 model. In particular, this method’sperformance for a set of events in other cycles is as good as that of the STOAand ISPM models. This gives us confidence in its application to other cycles.From the viewpoint of long-term periodicity for solar activity, it is expected thatthe database method can be applicable to the next solar cycle 24. However, thedatabase method also has its shortcomings. We do not take into account of theshort-time variations of coronal magnetic field, which will make the large-scalestructure of the heliospheric current sheet and background solar wind somewhatdeviate from the real situations. And these factors would induce some errors forprediction of the database method. Moreover, for simplicity, the phase of othersolar cycle does not well correspond to the one of cycle 23 for the applicationto other cycles. This will be considered in the future work. The present workprovides us a new method to predict the shock arrival time rapidly. Two shock propagation models are established to predict the arrival timeof interplanetary shocks at 1AU. One interplanetary shock propagation modelis built up based on 1D-HD equations by using Roe scheme. Another is a 1D-MHD shock propagation model by using the space-time conservation elementand solution element (CE/SE) method. Applying these models to solar eruptiveevents during the 23rd solar cycle to evaluate the forecasting skill, it is found thatour models could be practically equivalent to the other models in forecasting theshock arrival time. These results might demonstrate a potential capability of ourmodels in terms of real-time forecasting. Although these models are simple 1Dnumerical models, but they can predict the shock arrival time rapidly. Moreover,they were expected to forecast“no shock”by improving them in the future work.更多还原