共查询到19条相似文献，搜索用时 218 毫秒
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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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发生于2003年10～11月许许多多日地关系重大事件,西方称为万圣节日地事件或风暴(Halloween Events 或Halloween Storms),并予以特别关注.本文综述对这次日地重大事件的国际集会讨论和公开出版的文献,在太阳爆发方面包括：（1）太阳活动区与耀斑;（2）日冕物质抛射CMEs;（3）日冕激波;（4）太阳高能粒子SFPs;（5）活动区能量与面积、耀斑大小和CME速率.在日球层与地球物理效应方面,包括：（1）日球层响应;（2）大磁暴与宇宙线磁层效应;（3）热层与电离层效应;（4）白天极光、臭氧亏损;（5）中国学者工作.期望我国在此基础上积极开展工作和取得创新. 相似文献
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本文采用一种新的坐标系——耀斑-日球电流片坐标系,对1966—1982年间由耀斑-激波所引起的277个耀斑-地磁扰动事件进行了分析.初步结果是:1.耀斑-地磁扰动事件在该坐标系中相对日球电流片的随机分布呈高斯分布,极大值在电流片附近;2.当地球和耀斑位于日球电流片同侧时,地磁扰动事件频次远高于异侧;3.地磁扰动强弱在该坐标系中的分布,亦呈现了同侧高于异侧,且极大值多在日球电流片附近;4.耀斑-激波能流密度ρ_2V_2~3及其跃变量ρ_2V_2~3-ρ_1V_1~3在该坐标系中具有十分类似于相应磁扰水平的分布,其离散程度后者略大于前者. 根据本文的结果可以看出,对耀斑-地磁扰动研究来说,近太阳日球电流片的存在是一个重要的特征面,它对耀斑-地磁扰动的产生和强弱水平有重要影响,使太阳耀斑活动与地磁活动效应之间的对应关系变得复杂化了. 相似文献
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本文采用一种新的坐标系--耀斑-日球电流片坐标系,对1966-1982年间由耀斑-激波所引起的277个耀斑-地磁扰动事件进行了分析.初步结果是:1.耀斑-地磁扰动事件在该坐标系中相对日球电流片的随机分布呈高斯分布,极大值在电流片附近;2.当地球和耀斑位于日球电流片同侧时,地磁扰动事件频次远高于异侧;3.地磁扰动强弱在该坐标系中的分布,亦呈现了同侧高于异侧,且极大值多在日球电流片附近;4.耀斑-激波能流密度ρ2V23及其跃变量ρ2V23-ρ1V13在该坐标系中具有十分类似于相应磁扰水平的分布,其离散程度后者略大于前者. 根据本文的结果可以看出,对耀斑-地磁扰动研究来说,近太阳日球电流片的存在是一个重要的特征面,它对耀斑-地磁扰动的产生和强弱水平有重要影响,使太阳耀斑活动与地磁活动效应之间的对应关系变得复杂化了. 相似文献
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本文统计了第２２ 太阳活动周期间（１９９１ ～１９９５ 年） 发生的２５ 个太阳质子事件与太阳耀斑及日冕物质抛射（ＣＭＥ） 事件的关系 统计结果表明, 所有的太阳质子事件都与耀斑发生相关, 除２ 个质子事件（１９９４１０２０ 和１９９５１０２０ 日发生的太阳质子事件） 与ＣＭＥ发生无关, 其余质子事件也都与ＣＭＥ 相关 值得注意的是, 与质子事件相关的耀斑有１６ 个是双带耀斑, 其中包括与ＣＭＥ无关的２ 个事件的耀斑, 占总数的６４ ％ 上述统计结果证实了无论是太阳耀斑, 还是物质抛射, 它们对太阳质子事件的发生同样起着非常重要的作用 相似文献
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提出了一个新的太阳宇宙线日 -地传输的数学模型 ,它包括日冕粒子分布源和行星际传播方程 .根据对太阳宇宙线耀斑黑子群特征和耀斑相的观测 ,提出了多极性黑子湮没的两阶段日冕传输过程和传输方程 ,得到了与观测特征一致的日冕粒子分布源 .日冕传输的第一阶段 ,和太阳耀斑脉冲相的时间相当 ,加速粒子通过扩散很快均匀地分布在耀斑区 ,形成所谓快传播区 .第二阶段 ,加速粒子向快传播区以外的日冕区扩散并向行星际空间逃逸 ,形成慢传播过程 .日冕传输模型的数值结果和日冕传输的观测特征符合 .太阳宇宙线的行星际传播采用三维正交均匀各向异性方程描述 .最后把模型的数值结果与 1 997年 9月 2 4日事件的SOHO（SolarandHeliosphericObservatory）观测资料作了比较 .能较好地符合 . 相似文献
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一、引言自海尔（G.E.Hale）提出太阳耀斑活动的特性为日地关系的重要关鍵这一問題后,近30年来天文学家、地球物理学家对于耀斑所引起的一系列的現象,进行了許多研究工作。爱立生（M.A.Ellison）曾将研究太阳耀斑本身及其所引起的地球物理現象等工作,就其性貭綜合为九个方面.其中联系到地磁方面的为与耀斑几乎同时发生的紫外綫輻射所引起的“鈎扰”,和由于耀斑发射出来的微粒子流在1-2天以后达到地球而引起的“磁暴”. 相似文献
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We study the geometry of magnetic fluctuations in a CIR observed by Pioneer 10 at 5 AU between days 292 and 295 in 1973. We apply the methodology proposed by Bieber et al. to make a comparison of the relative importance of two geometric arrays of vector propagation of the magnetic field fluctuations: slab and two-dimensional (2D). We found that inside the studied CIR this model is not applicable due to the restrictions imposed on it. Our results are consistent with Alfvenic fluctuations propagating close to the radial direction, confirming Mavromichalaki et al.’s findings. A mixture of isotropic and magnetoacoustic waves in the region before the front shock would be consistent with our results, and a mixture of slab/2D and magnetoacoustic waves in a region after the reverse shock. We base the latter conclusions on the theoretical analysis made by Kunstmann. We discuss the reasons why the composite model can not be applied in the CIR studied although the fluctuations inside it are two dimensional. 相似文献
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《地震工程与结构动力学》2018,47(6):1478-1495
In soil‐structure interaction modeling of systems subjected to earthquake motions, it is classically assumed that the incoming wave field, produced by an earthquake, is unidimensional and vertically propagating. This work explores the validity of this assumption by performing earthquake soil‐structure interaction modeling, including explicit modeling of sources, seismic wave propagation, site, and structure. The domain reduction method is used to couple seismic (near‐field) simulations with local soil‐structure interaction response. The response of a generic nuclear power plant model computed using full earthquake soil‐structure interaction simulations is compared with the current state‐of‐the‐art method of deconvolving in depth the (simulated) free‐field motions, recorded at the site of interest, and assuming that the earthquake wave field is spatially unidimensional. Results show that the 1‐D wave‐field assumption does not hold in general. It is shown that the way in which full 3‐D analysis results differ from those which assume a 1‐D wave field is dependent on fault‐to‐site geometry and motion frequency content. It is argued that this is especially important for certain classes of soil‐structure systems of which nuclear power plants subjected to near‐field earthquakes are an example. 相似文献
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Results of studying the ionospheric response to solar flares, obtained based on the incoherent scatter radar observations
of the GPS signals and as a result of the model simulations, are presented. The method, based on the effect of partial “shadowing”
of the atmosphere by the globe, has been used to analyze the GPS data. This method made it possible to estimate the value
of a change in the electron content in the upper ionosphere during the solar flare of July 14, 2000. It has been shown that
a flare can cause a decrease in the electron content at heights of the upper ionosphere (h > 300 km) according to the GPS data. Similar effects in the formation of a negative disturbance in the ionospheric F region
were also observed during the solar flares of May 21 and 23, 1967, at the Arecibo incoherent scatter radar. The mechanism
by which negative disturbances are formed in the upper ionosphere during solar flares has been studied based on the theoretical
model of the ionosphere-plasmasphere coupling. It has been shown that an intense ejection of O+ ions into the above located plasmasphere under the action of a sharp increase in the ion production rate and the thermal
expansion of the ionospheric plasma cause the formation of a negative disturbance in the electron concentration in the upper
ionosphere. 相似文献
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Broadband ground motion simulation using a hybrid approach of the May 21, 2021 M7.4 earthquake in Maduo,Qinghai, China 
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下载免费PDF全文 Yijun Liu Xiaofen Zhao Zengping Wen Jie Liu Bo Chen Chunyao Bu Chao Xu 《地震科学（英文版）》2023,36(3):175-199
In this study, the broadband ground motions of the 2021 M7.4 Maduo earthquake were simulated to overcome the scarcity of ground motion recordings and the low resolution of macroseismic intensity map in sparsely populated high-altitude regions. The simulation was conducted with a hybrid methodology, combining a stochastic high-frequency simulation with a low-frequency ground motion simulation, from the regional 1-D velocity structure model and the Wang WM et al.(2022) source rupture model,respect... 相似文献
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空间飞船Helios 1和Helios 2的磁场探测发现,太阳风高速流中磁场脉动在低频区的能谱的谱指数是随日心距离r而变化的,谱密度的空间梯度是随频率f而变化的,现有关于行星际磁场脉动的理论都不能解释上述现象。本文提出了一个计算行星际磁场能谱径向发展的理论模式。假设在不同频率的脉动之间有由低频向高频传输的能流存在,在这一基础上建立了谱方程,并得到了谱方程的数值解。数值解表明,由0.3AU至1AU,低频区的谱指数增加,而高频区的谱指数近似保持为常数（-1.6）;低频区平均谱密度随着日心距离的变化为r-3.5,在高频区为r-4.1,所有这些都与观测相符合。串级的能量很可能最后传输到质子回旋频率范围,由于回旋共振而耗散,最后加热太阳风质子。这一模式有可能用来计算太阳风的加速问题。 相似文献
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The results of a three-dimensional MHD simulation and data obtained using specialized spacecraft made it possible to construct
an electrodynamic model of solar flares. A flare results from explosive magnetic reconnection in a current sheet above an
active region, and electrons accelerated in field-aligned currents cause hard X rays on the solar surface. In this review,
we considered works where the boundary and initial conditions on the photosphere were specified directly from the magnetic
maps, obtained by SOHO MDI in the preflare state, in order to simulate the formation of a current sheet. A numerical solution
of the complete set of MHD equations, performed using the new-generation PERESVET program, demonstrated the formation of several
current sheets before a series of flares. A comparison of the observed relativistic proton spectra and the simulated proton
acceleration along a magnetic field singular line made it possible to estimate the magnetic reconnection rate during a flare
(∼107 cm s−1). Great flares (of the X class) originate after an increase in the active region magnetic flux up to 1022 Mx. 相似文献
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Pedro Alves Costa Rui Calçada António Silva Cardoso Anders Bodare 《Soil Dynamics and Earthquake Engineering》2010
The main objectives of this paper are the evaluation of the relevance of the non-linear behaviour of the soil on the track response and the validation of a methodology, which includes these effects through an equivalent linear analysis. The proposed numerical model is based on 2.5D finite/infinite elements method, coupled with an iterative procedure in order to obtain an agreement between the strain levels and the dynamic properties of the materials. In order to validate the model, the case study of Ledsgard was simulated, and the experimental and numerical results of displacements of the track were compared, considering several circulation speeds for the X2000 train. From the results, it is possible to recognize that the stiffness degradation, function of the strain level, plays a relevant role for the case of high-speed railway lines on soft ground. Moreover, the simulations developed with the proposed methodology provided similar results to those observed, independently of the train speed, contrary to what was obtained when the elastic linear model was used. 相似文献
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中高层钢筋混凝土异形柱框架结构试验与理论研究 总被引：8，自引：0，他引：8
对-1/6比例12层大开间钢筋混凝土异形柱框架结构模型进行了振动台试验，探讨结构的地震反应和破坏形态，采用杆模型编制了钢筋混凝土异形柱框架结构的弹塑性时程分析程序，经比较，计算结果与试验值吻合较好，探讨了肢长肢厚比对该体系结构性能的影响，并提出了相应的设计建议。 相似文献
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Coronal mass ejections (CMEs) and solar flares are the large-scale and most energetic eruptive phenomena in our solar system and able to release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind. When these high-speed magnetized plasmas along with the energetic particles arrive at the Earth, they may interact with the magnetosphere and ionosphere, and seriously affect the safety of human high-tech activities in outer space. The travel time of a CME to 1 AU is about 1–3 days, while energetic particles from the eruptions arrive even earlier. An efficient forecast of these phenomena therefore requires a clear detection of CMEs/flares at the stage as early as possible. To estimate the possibility of an eruption leading to a CME/flare, we need to elucidate some fundamental but elusive processes including in particular the origin and structures of CMEs/flares. Understanding these processes can not only improve the prediction of the occurrence of CMEs/flares and their effects on geospace and the heliosphere but also help understand the mass ejections and flares on other solar-type stars. The main purpose of this review is to address the origin and early structures of CMEs/flares, from multi-wavelength observational perspective. First of all, we start with the ongoing debate of whether the pre-eruptive configuration, i.e., a helical magnetic flux rope (MFR), of CMEs/flares exists before the eruption and then emphatically introduce observational manifestations of the MFR. Secondly, we elaborate on the possible formation mechanisms of the MFR through distinct ways. Thirdly, we discuss the initiation of the MFR and associated dynamics during its evolution toward the CME/flare. Finally, we come to some conclusions and put forward some prospects in the future. 相似文献