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1.
本文在分析行星际激波传播的空间特性的基础上,提出了一种物理模式加统计的预报方法。对1975-1982年间58个耀斑-IPS激波事件是否引起地球磁暴急始进行预报的结果如下:有无磁暴急始发生的报准率是77.6％,虚报率为22.4％;磁暴急始发生时间的预报准确性,大多在±10小时内。这表明利用IPS观测进行磁暴急始预报有很大的潜力和现实可能性。 相似文献
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3.
行星际激波与地球磁层相互作用通常会导致日侧极光活动增强,随后沿着极光卵的晨昏两侧向夜侧扩展的激波极光.行星际激波也可能直接导致夜侧扇区极光活动增强,甚至沉降粒子能通量的数量级可以与典型亚暴相比拟.本文首次利用我国南极中山站和北极黄河站连续多年积累的极光观测数据,对行星际激波与地球磁层相互作用期间地面台站在夜侧扇区(18—06MLT)观测的极光响应进行了分析.对18个极光观测事件的分析结果表明:行星际激波与磁层相互作用可以在夜侧触发极光爆发和极光微弱增强或静态无变化事件;太阳风-磁层能量耦合的效率以及磁层空间的稳定性决定着行星际激波能否触发极光爆发. 相似文献
4.
本文提出一种用于研究太阳瞬变扰动在日球空间传播的新坐标系--瞬变源-日球电流片坐标系,并运用该坐标系以瞬变源耀斑为例,分析研究了由地球近空飞船观测到的277个耀斑-激波事件,发现:1.引起行星际激波和地球物理事件的大耀斑（Hα≥2,持续时间>半小时）的频数在耀斑-日球电流片坐标系中呈高斯分布,极值在电流片附近,那种在日面坐标系中随日面纬度呈双峰形的分布看不到了;2.当地球观测者和耀斑位于日球电流片同侧时,耀斑事件频次明显高于它们分处不同侧时的情形;3.激波参数（速度、磁场、密度和温度）呈现了同侧高于异侧,强激波多在同侧观测到;4.激波沿日球电流片方向的传播具有一定优势.上述结果表明,日球电流片的存在对瞬变扰动,如耀斑-激波在日球空间,特别是近太阳的传播可能具有重要影响. 相似文献
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地球外辐射带是一个高度动态变化的空间环境,辐射带电子通量的变化在磁暴期间尤为明显.要分析潜在的电子动态变化机制,需要排除绝热效应产生的影响.在以三个绝热不变量组成的相空间坐标中,利用相空间密度(PSD)可以反映电子的真实加速和损失情况.本文详细分析两颗范艾伦卫星和三颗GPS导航卫星在2013年3月的同步电子通量观测数据,发现在3月17日磁暴期间,当太阳风动压增大、行星际磁场南向时,辐射带电子通量会发生骤降.进一步将电子通量转换成电子相空间密度并利用不同第一、第二绝热不变量(μ,K)组合条件下PSD径向分布的差异性,深入探究磁暴期间辐射带电子的动态变化机制.结果表明:磁暴初期由于电子的局地加速导致PSD不断上升;磁暴主相期间,由于磁层顶阴影效应以及伴随的向外径向扩散损失导致PSD快速降低;位于不同空间位置的多颗卫星观测为明晰辐射带电子动态物理过程提供了重要的便利. 相似文献
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2003年11月20日磁暴主相期间,Cluster卫星正好处在黄昏侧的磁鞘附近.在主相期间磁鞘磁场Bz分量大约为-60 nT,这和ACE卫星观测值基本一致.同时,磁鞘中的离子速度分布对磁鞘中的磁场方向有很强的依赖性.行星际电场Ey在磁鞘中大约是50 mV/m.磁鞘中这些极端的磁场,电场和离子的流动驱动了迄今23个太阳活动周期中最大的磁暴,其Dst指数是-472 nT.Cluster卫星观测发现磁鞘中离子的数密度比较低,这可能是由磁云经过地球时太阳风的低密度造成的.磁鞘中能量范围为1～10 keV的H+,He+和He2+的数密度主要是由磁鞘中太阳风的数密度决定的.同时,对磁鞘中存在大量的1～10 keV氧离子进行了讨论.在极端的南向行星际磁场条件下,磁层顶受到很强的压缩.氧离子可以利用较大的回旋半径,在强压缩的磁层顶和磁鞘对流的共同影响下进入磁鞘.这也表明了磁层对极端行星际条件的一种响应.Cluster卫星在11月20日磁暴事件中的观测研究,对进一步全面认识大磁暴事件有很重要的作用. 相似文献
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2003年10～11月的大磁暴 总被引：3，自引：2，他引：3
分析了引起2003年10～11月发生的3个特大磁暴的太阳活动、行星际扰动以及中国东部地磁台链记录到的地面磁场变化。结果表明,这3个特别大的磁暴是由太阳质量抛射事件引起的。太阳向着地球喷发出的大量等离子体引起的强烈太阳风扰动和持续长时间的南向行星际磁场与磁层相互作用形成了特别大的磁暴。ACE卫星、GOES卫星以及地面地磁台站较完整地记录了这3次日地扰动传输过程。对于每一个磁暴,中国东部地磁台链记录到的H分量变化形态一致,纬度最高的满洲里地磁台H幅度最大,而其他台站的幅度与纬度无明显关系,这表明磁暴的发展不完全由赤道环电流引起,在这样强烈的磁暴期间,磁层内的电流体系非常复杂。 相似文献
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利用172-182年IMP-8飞船的太阳风观测资料和相应地磁活动性指数Dst和AE,研究了43个南向行星际磁场事件期间太阳风和磁层的耦合问题. 与这43个事件对应的地磁暴是中等的和强的磁暴(Dst＜-50nT). 结果表明:(1) 在43个事件中有11个(约占25.6髎)紧随激波之后,18个处于激波下游流场中(占42髎),其余14个(占33髎)和激波没有关连. 绝大多数事件都伴有太阳风动压和总磁场强度的增加;(2) 当行星际晨昏向电场强度EI＞-4mV/m时,只引起磁亚暴,对Dst指数没有明显影响. 仅当EI＜-5mV/m时,磁亚暴和磁暴才会同时出现;(3) 太阳风动压的增加会增强能量向环电流的输入,但不是密度和速度单独起作用,而是以PK=ρV2的组合形式影响能量的输入;(4) 虽然行星际磁场(IMF)南向分量BZ对太阳风和磁层的耦合起着关键作用,但IMF的BX和BY分量相对于BZ的大小对太阳风向磁层的能量传输也有一定影响. 当BX、BY相对BZ较大时能量耦合加强. 相似文献
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本文利用低高度极轨卫星NOAA/POES的观测数据,对2003年Hallowe'en磁暴期间新质子带的形成和损失机制做了细致的研究和分析.结果表明新质子带的形成是诸多因素共同作用的结果.包括强太阳质子事件(Solar Proton Events,SPEs)、大的地磁暴和行星际激波.所有这些因素构成了新质子带形成的前提条件,尤其是行星际激波是形成新质子带不可缺少的因素.此外本文提出了磁暴主相对高能质子注入磁层稳定捕获区起到重要贡献.本文还运用绝热捕获判据分析了新质子带的损失机制,证明了由于磁暴期间环电流积累造成磁场大的扰动,破坏绝热不变量的守恒,导致新质子带粒子的损失. 相似文献
10.
本文利用低高度极轨卫星NOAA/POES的观测数据,对2003年Hallowe'en磁暴期间新质子带的形成和损失机制做了细致的研究和分析. 结果表明新质子带的形成是诸多因素共同作用的结果,包括强太阳质子事件（Solar Proton Events, SPEs）、大的地磁暴和行星际激波.所有这些因素构成了新质子带形成的前提条件,尤其是行星际激波是形成新质子带不可缺少的因素.此外本文提出了磁暴主相对高能质子注入磁层稳定捕获区起到重要贡献.本文还运用绝热捕获判据分析了新质子带的损失机制,证明了由于磁暴期间环电流积累造成磁场大的扰动, 破坏绝热不变量的守恒,导致新质子带粒子的损失. 相似文献
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利用Morlet小波变换方法对北京宇宙线台站的地面宇宙线强度在地磁暴前后的变化特征进行分析,得到:1)在平静期,北京宇宙线数据存在准24h周期性的特征,且通过分析周期为12h的Morlet小波"模",发现值稳定,且小于0.6;2)以90天为时间窗口,对2004年7月地磁暴前后的小波频谱变化进行详细分析,发现当发生大地磁暴时,宇宙线的静日准24h周期被打破,其他周期的波动开始增强.进一步研究发现,周期12h的波动在大地磁暴数小时到1天左右会出现显著增强,这一现象在2001、2002和2004年期间的大地磁暴前得到验证.3)Morlet小波"模"数据的急速增大是发生地磁暴的先兆特征,当小波模变化达到一定的阈值就可能发生大磁暴.本文分析了周期为12h时小波的模数据,对强地磁暴事件进行统计,选定阈值0.6,并通过2003年的6次大地磁暴进行预报验证,结果表明该方法不仅能够对大地磁暴事件进行预报,而且提前量满足预报需求,为基于宇宙线实测数据预报地磁暴方法提供了重要基础. 相似文献
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Based on the WIND and GOES satellite data on the solar wind and IMF parameters and the data on the surface magnetic field,
it has been indicated that the secondary MHD rarefaction wave can affect the geomagnetic field during a storm sudden commencement
(SSC) event. The secondary rarefaction wave originates in the magnetosheath when the shock wave interacts with the Earth’s
magnetosphere. 相似文献
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日冕物质抛射(CME)的规模和对地有效性是地磁暴预报中重点关注的特征.本项研究的目的是通过对行星际高能质子通量和能谱的特征与演化规律的分析,得到CME对粒子的加速能力,评估CME可能对地磁场造成的影响.在工作中,统计分析了ACE/EPAM的1998-2010年的质子数据,对质子能谱进行了拟合,得到了能谱指数,并对能谱指数及其变化特征所对应的CME和地磁暴进行了相关统计.通过研究发现:(1)能谱指数随着太阳活动水平而变化,高年最大,达到-2.6,而且涨落幅度也达到±0.4,而在太阳活动低年则稳定在-3.0左右;(2)CME对粒子的加速对应着能谱指数的升高,幅度达到20%时,CME引起地磁暴的可能性较大;(3)冕洞高速流到达地球时,高能质子通量也会升高,但能谱指数同时会有下降;(4)以2004年全年的能谱指数为例,对能谱指数在地磁暴预报中的应用进行了评估,结论认为,能谱指数的升高是CME引发地磁暴的必要条件,可以作为地磁暴预报的参数使用. 相似文献
14.
We investigate the features of the planetary distribution of wave phenomena (geomagnetic pulsations) in the Earth’s magnetic shell (the magnetosphere) during a strong geomagnetic storm on December 14–15, 2006, which is untypical of the minimum phase of solar activity. The storm was caused by the approach of the interplanetary magnetic cloud towards the Earth’s magnetosphere. The study is based on the analysis of 1-min data of global digital geomagnetic observations at a few latitudinal profiles of the global network of ground-based magnetic stations. The analysis is focused on the Pc5 geomagnetic pulsations, whose frequencies fall in the band of 1.5–7 mHz (T ～ 2–10 min), on the fluctuations in the interplanetary magnetic field (IMF) and in the solar wind density in this frequency band. It is shown that during the initial phase of the storm with positive IMF Bz, most intense geomagnetic pulsations were recorded in the dayside polar regions. It was supposed that these pulsations could probably be caused by the injection of the fluctuating streams of solar wind into the Earth’s ionosphere in the dayside polar cusp region. The fluctuations arising in the ionospheric electric currents due to this process are recorded as the geomagnetic pulsations by the ground-based magnetometers. Under negative IMF Bz, substorms develop in the nightside magnetosphere, and the enhancement of geomagnetic pulsations was observed in this latitudinal region on the Earth’s surface. The generation of these pulsations is probably caused by the fluctuations in the field-aligned magnetospheric electric currents flowing along the geomagnetic field lines from the substorm source region. These geomagnetic pulsations are not related to the fluctuations in the interplanetary medium. During the main phase of the magnetic storm, when fluctuations in the interplanetary medium are almost absent, the most intense geomagnetic pulsations were observed in the dawn sector in the region corresponding to the closed magnetosphere. The generation of these pulsations is likely to be associated with the resonance of the geomagnetic field lines. Thus, it is shown that the Pc5 pulsations observed on the ground during the magnetic storm have a different origin and a different planetary distribution. 相似文献
15.
地磁暴的行星际源研究是了解及预报地磁暴的关键因素之一.本文研究了2007-2012年间的所有Dstmin ≤-50 nT的中等以上地磁暴,建立了这些地磁暴及其行星际源的列表.在这6年中,共发生了51次Dstmin≤-50 nT的中等以上地磁暴,其中9次为Dstmin≤-100 nT的强地磁暴事件.对比上一活动周相同时间段发现,在这段太阳活动极低的时间,地磁暴的数目显著减少.对这些地磁暴行星际源的分析表明,65%的中等以上地磁暴由与日冕物质抛射相关的行星际结构引起,31%的地磁暴由共转相互作用区引起,这与以前的结果一致.特别的,在这个太阳活动极低时期内,共转相互作用区没有引起Dstmin≤-100 nT的强地磁暴,同时,日冕物质抛射相关结构也没有引起Dstmin≤-200 nT的超强地磁暴.以上结果表明极低太阳活动同时导致了共转相互作用区和日冕物质抛射地磁效应的减弱.进一步,分析不同太阳活动期间地磁暴的行星际源发现:在太阳活动低年(2007-2009年),共转相互作用区是引起地磁暴的主要原因; 而在太阳活动上升期和高年(2010-2013年),大部分(75%,30/40)的中等以上地磁暴均由日冕物质抛射相关结构引起. 相似文献
16.
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. 相似文献
17.
将1996—2015年太阳黑子数、强磁暴和M_S≥7.0亚洲浅源地震,按Dst指数大小对磁暴进行分类和统计,按震级大小对地震进行分类统计,结果发现,在1996—2015年太阳活动周下降年易发生大磁暴,且M_S≥7.0地震年发生率明显高于太阳活动周上升年、极大年和极小年。 相似文献
18.
《Journal of Atmospheric and Solar》1999,61(13):993-1000
Hourly equatorial Dst (H) values for a few sudden commencement great geomagnetic storms recorded during the solar cycle 22 are plotted for 72 h of storm time and critically examined. Magnetic records taken at selected low latitude Indian stations are also scrutinised for finer details like SSCs, SIs and other fluctuations. Unusually prolonged main phases lasting more than 20 h characterize the two great storms of 13 March 1989 and 24 March 1991. A second SSC/SI pair, occurring some hours after the first main SSC, has also been identified in these storms. Only the great storm of 28 October 1991, with two SSCs and a main phase duration of 21 h, could be studied in conjunction with simultaneous interplanetary data, including Bz changes. Double negative Bz changes correlate well with the extended and enhanced main phase of this storm. Successive magnetic clouds preceded by interplanetary shock waves could generate such great magnetic storms in association with southward IMF changes. 相似文献
19.
Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model 总被引：1，自引：0，他引：1
Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N2] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes) above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The calculated zonal electric field disturbances also help to create the positive ionospheric disturbances both at middle and low latitudes. Minor contributions arise from the general density enhancement of all constituents during geomagnetic storms, which favours ion production processes above ion losses at fixed height under day-light conditions. 相似文献
20.
S. A. Grib 《Geomagnetism and Aeronomy》2013,53(4):424-429
The motion of the MHD nonlinear shock in the Earth’s magnetosphere is considered in the scope of magnetic hydrodynamics. This wave comes from the solar wind and is refracted into the magnetosphere, generating a fast return rarefaction wave. It has been indicated that a wave refracted into the magnetosphere is a weak fast dissipative shock, propagating in magnetospheric plasma at a velocity higher than its propagation velocity in a solar wind stream. The wave motion near the Earth-Sun line with regard to the effect of the geomagnetic field transverse component is described. In this case, shock damping follows the generalized Crussard-Landau law and a wave retains its shock character up to the plasmapause, interacting with this region when an arbitrary MHD discontinuity is disintegrated. It is stated that an MHD shock loses its shock character when moving in a strongly inhomogeneous plasma within the plasmasphere and a weak shock reflected from the plasmapause can combine with a return secondary shock in the magnetosheath, promoting the experimentally observed backward motion of the bow shock front. 相似文献