共查询到19条相似文献,搜索用时 125 毫秒
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地球磁尾等离子体片在太阳风-磁层耦合过程中起着重要的作用,其中冷而密的等离子体片是地磁活动平静期太阳风等离子体进入磁层的重要区域.以往的研究通常没有利用局地探测数据针对冷而密的等离子体片发生率在地心太阳磁层坐标系(GSM)中xy平面分布的统计分析.本文利用GEOTAIL卫星1996-2016年的局地测量数据,给出了等离子体片密度、温度及冷而密的等离子体片发生率的二维分布.与温度具有晨昏对称分布不同,等离子体片数密度呈现明显的晨昏不对称性,并且冷而密的等离子体片发生率在晨侧较高. 相似文献
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根据磁层粒子动力学理论, 通过偶极磁场模型验证利用三维试验粒子轨道方法模拟近地球区(r < 8Re)带电粒子运动特征的可靠性. 在此基础上, 以太阳风和磁层相互作用的全球MHD模拟结果为背景, 利用三维试验粒子轨道方法, 对非磁暴期间南向行星际磁场背景下太阳风离子注入磁层的情形进行数值模拟, 并对北向行星际磁场背景下太阳风离子注入极尖区以及内磁层的几种不同情形进行了单粒子模拟. 模拟结果反映了南向和北向行星际磁场离子向磁层的几种典型输入过程, 揭示出行星际磁场南向时太阳风粒子在磁层内密度分布的晨昏不对称性以及其在磁鞘和磁层内的大致分布, 并得出统计规律. 模拟结果与理论预测和观测结论相一致, 且通过数值模拟发现, 行星际磁场北向时靠近极尖区附近形成的非典型磁镜结构对于能量粒子经由极尖区注入环电流区域过程有重要的影响和作用. 相似文献
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本文利用东亚地区12个低纬电离层台站的测高仪观测数据,对1978年8月27日发生的一次曲型磁暴期间电离层峰值高度和密度的变化进行了分析。采用滑动平均区分开电离层中不同时间尺度的扰动,分析了影响中低纬度电离层暴的几种扰动形态特征,并对其物理机制进行了讨论。结果表明:伴随磁暴急始的磁层压缩,电离层中表现出峰值密度增加和峰值高度下降;磁暴主相期间热层大气暴环流及其所引起的中性大气成分变化控制着电离层的大 相似文献
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嫦娥一号卫星太阳风离子探测器离子流量反演太阳风参数与初步结果分析 总被引:2,自引:0,他引:2
嫦娥一号卫星(Chang'E-1)上搭载的两台太阳风离子探测器(SWID-A/B)是国际上首次在200 km极月轨道观测等离子体环境的探测仪器.SWID-A/B的科学目标是探测月球附近等离子体与月球的相互作用,获得月球附近的太阳风速度、密度和温度.太阳风离子探测器的观测数据是各能量成分离子流量的直接反映,包含了太阳风离子的速度、密度和温度信息.本文设计了一种利用离子流量数据反演太阳风速度、密度和温度的算法,并通过模拟太阳风离子注入探测器的过程,验证了算法的可行性.对月球附近太阳风离子基本特征的分析研究表明,在太阳活动低年,空间环境扰动水平相对较低时,行星际太阳风运动到月球附近后依然保持着相同的变化趋势;太阳风离子的速度和密度与在上游行星际空间时相近;太阳风离子的温度则比在上游行星际空间时高103 K. 相似文献
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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vs w、温度T sw、数密度Dsw、磁场B和动压Psw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。 相似文献
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行星际起伏向磁层顶的输运 总被引:1,自引:1,他引:0
时间尺度为分钟数量级的太阳风速度和行星际磁场大幅度扰动实际上始终存在于行星际空间的。这些扰动一直传输到紧贴磁层边界面外侧的区域。它们在磁鞘等离子体和磁层顶的相互作用过程中可能起很重要的作用。行星际起伏中的磁场分量在通过地球弓激波时首先经历一次跳跃,然后一部分扰动被带到磁层边界面处。在边界面附近磁场扰动幅度被大大地放大了。弓激波上游的太阳风条件控制了放大因子。本文所作的数值模拟研究结果表明,如果上游有大幅度的扰动,在边界面附近就有大幅度的Alfven起伏的磁场分量。当上游磁场接近垂直于日地联线时,放大因子变得相当大,而且放大因子随上游的等离子体β值和/或Alfven马赫数的增加而增加。上游各向异性对放大因子的影响不大。在磁层边界附近存在大幅度起伏表明这里不存在稳定的片流。 相似文献
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利用行星际太阳风参数与太阳活动指数、地磁活动指数、电离层总电子含量格点化地图数据,首次基于一种能处理时间序列的深度学习递归神经网络(Recurrent Neural Network,RNN),建立提前24h的单站电离层TEC预报模型.对北京站(40°N,115°E)的预测结果显示,RNN对扰动电离层的预测误差低于反向传播神经网络(Back Propagation Neural Network,BPNN)0.49~1.46TECU,将太阳风参数加入预报因子模型后对电离层正暴预测准确率的提升可达16.8%.RNN对2001和2015年31个强电离层暴预报的均方根误差比BPNN低0.2TECU,将太阳风参数加入RNN模型可使31个事件的平均预报误差降低0.36~0.47TECU.研究结果表明深度递归神经网络比BPNN更适用于电离层TEC的短期预报,且在预报因子中加入太阳风数据对电离层正暴的预报效果有明显改善. 相似文献
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Energetic oxygen ions in the magnetosheath in the negative BZ phase of the CME on January 10, 1997 总被引:1,自引:0,他引:1
Q.-G. Zong B. Wilken S.Y. Fu T. Doke S. Kokubun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2000,25(12):2421-2424
Energetic oxygen ion flux intensifications were observed by the HEP/LD instrument on board the GEOTAIL satellite thoughout the Bz negative phase of the CME event on January 10, 1997. At this time, the spacecraft was moving in the magnetosheath at 1500 LT on a magnetopause skimming segment of its orbit. The very steady southward magnetic field in the magnetosheath (negative Bz of the CME) was highly inclined forming an angle of 45° with respect to the north direction. The observed oxygen enhancements in the magnetosheath show anisotropic angular distributions which occupy a varying fraction of the unit sphere. These distributions became particularly narrow during the passage of a solar wind pressure pulse between between 1050 and 1113 UT. The details of the angular distributions in the magnetosheath favour a leakage model, although the reconnection model cannot be denied. 相似文献
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Yekoye Asmare Tariku 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(7):2066-2074
This paper mainly discusses the improvement of performance of the International Reference Ionosphere (IRI) model in estimating the variation of the Vertical Total Electron Content (VTEC) over the mid latitude American regions during the relatively low (2008–2010) and relatively high (2012) solar activity years. This has been conducted employing the VTEC values obtained from the dual frequency ground based Global Positioning System (GPS) receivers located at Mineral Area Community College, MACC (37.85°N, 269.52°W) and Mississippi County Airport, MAIR (36.85°N, 270.64°W), and the latest versions of the IRI online model (IRI 2007, IRI 2012 and IRI 2016). The study mainly focuses to compare the trend of variability of the monthly and seasonal modeled VTEC values (IRI 2007 VTEC, IRI 2012 VTEC and IRI 2016 VTEC) with the corresponding measured VTEC values (GPS VTEC). The overall results show that the IRI VTEC values (almost in all versions of the model) are generally smaller than the GPS VTEC except after about 15:00 UT (09:00 LT) in the December solstice when the Sun shifts to the high solar activity. On the contrary, overestimations of the VTEC values by the model are observed in traversing from the low solar activity (2008) to high solar activity (2012) phase, especially after about 15:00 UT (09::00 LT) with the IRI 2016 version showing the highest. In general, the IRI 2007 and IRI 2012 versions show similar monthly and seasonal underestimations or overestimations showing that the two versions have almost similar performance. The IRI 2016 version is generally better in capturing both the diurnal and arithmetic mean GPS VTEC values with some exceptional months and seasons as compared to those of the IRI 2007 and IRI 2012 versions. 相似文献
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分析了2004年3月13日12:15到12:25UT期间TC-1和Cluster卫星簇的磁通门磁力计(FGM)和电子/电流试验仪(PEACE)的联合观测数据.在此期间,TC-1卫星位于日下点以南的磁层顶附近的磁鞘中,并在12:19UT左右观测到了一个典型的先正后负的磁鞘磁通量传输事件(FTE);而Cluster卫星簇位于北半球日侧高纬磁层项附近,并于12:23UT左右穿出磁层顶进入磁鞘,且在12:21 UT左右也观测到了一个典型的先正后负的磁层FTE.比较分析发现此两个FTE具有类似的磁场结构和等离子体特征,可能是同一个北向运动的FTE先后被TC-1和Cluster卫星观测到.利用Cluster 4颗卫星的多点同时观测数据,采用最小方向微分法和时空微分方法,推断Cluster卫星观测的这个FTE是尺度大小约为1.21Re的准二维结构,其运动方向为东北方向,与Cooling模型预测方向基本一致.利用Cooling模型的预测,推算了TC-1卫星在12:19UT观测的FTE的运动速度和尺度,进而得出随着通量管的极向运动,其速度和尺度均有所增加. 相似文献
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O.J. Olwendo P. Baki P.J. Cilliers C. Mito P. Doherty 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
This paper presents an analysis of the Total Electron Content (TEC) derived from the International GNSS Service receiver (formerly IGS) at Malindi (2.9°S, 40.1°E), Kenya for the periods 2004–2006 during the declining phase of solar cycle 23. The diurnal, monthly and seasonal variations of the TEC are compared with TEC from the latest International Reference Ionosphere model (IRI-2007). The GPS–TEC exhibits features such as an equatorial noon time dip, semi-annual variations, Equatorial Ionization Anomaly and day-to-day variability. The lowest GPS–TEC values are observed near the June solstice and September equinox whereas largest values are observed near the March equinox and December solstice. The mean GPS–TEC values show a minimum at 03:00 UT and a peak value at about 10:00 UT. These results are compared with the TEC derived from IRI-2007 using the NeQuick option for the topside electron density (IRI–TEC). Seasonal mean hourly averages show that IRI-2007 model TEC values are too high for all the seasons. The high prediction primarily occur during daytime hours till around midnight hours local time for all the seasons, with the highest percentage deviation in TEC of more 90% seen in September equinox and lowest percentage deviation in TEC of less than 20% seen in March equinox. Unlike the GPS–TEC, the IRI–TEC does not respond to geomagnetic storms and does overestimate TEC during the recovery phase of the storm. While the modeled and observed data do correlate so well, we note that IRI-2007 model is strongly overestimating the equatorial ion fountain effect during the descending phase of solar cycle, and this could be the reason for the very high TEC estimations. 相似文献
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Spatial distribution of the magnetosheath ion flux 总被引:1,自引:0,他引:1
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(12):2751-2756
The magnetosheath plays a crucial role in solar wind-magnetosphere interaction because it is the magnetosheath magnetic field and plasma that interact with the magnetopause and magnetosphere, not the unshocked solar wind. We are presenting ion flux measurement statistics at both the dawn and dusk flanks of the magnetosheath and their comparison with a gasdynamic magnetosheath model. The study is based on three years of INTERBALL-1 measurements supported by simultaneous WIND solar wind and magnetic field observations. Statistical processing has shown (1) the limitations of the gasdynamic model, (2) the conditions favorable for the creation of a plasma depletion layer adjacent to the flank magnetopause, (3) strong dawn-dusk asymmetry of the ion fluxes, and (4) an evidence for the presence of a slow mode front adjacent to the magnetopause. 相似文献
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2004年10月12日, 在01:30---04:30 UT期间, 位于向阳侧磁层顶附近的Geotail卫星探测到行星际磁场为持续南向. 此太阳风条件驱动了一个小磁暴, Sym-H指数在04:12 UT达到最小值-33nT. 在磁暴主相期间, AE指数维持在较高的水平, 其最大值达400nT. 02:00---03:00 UT期间, TC-1卫星在近地磁尾(-10.6, 3.2, -0.1)Re处观测到明显的亚暴膨胀相特征和磁场偶极化过程. 在偶极化前1min, 有较强的(vx<-100 km/s)持续时间超过3min的尾向流发生. 分析发现该尾向流具有低温、高密度和沿磁场流动的特点, 这说明尾向流具有来源于电离层风的特征. 尾向流期间, TC-1观测的磁场分量Bx和总的磁场强度增加, 磁倾角减小, 磁场结构变成非偶极型, 说明尾向流对磁场结构有一定的影响, 文中尝试给出了相应的物理解释. 观测表明, 该事例中的近地磁尾尾向流可能对磁场偶极化过程的发生有重要意义. 相似文献
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D.V. Phanikumar Y.-S. Kwak A.K. Patra A.K. Maurya Rajesh Singh S.-M. Park 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
In this paper, we analyze VLF signals received at Busan to study the the D-region changes linked with the solar eclipse event of 22 July 2009 for very short (∼390 km) transmitter–receiver great circle path (TRGCP) during local noon time 00:36–03:13 UT (09:36–12:13 KST). The eclipse crossed south of Busan with a maximum obscuration of ∼84%. Observations clearly show a reduction of ∼6.2 dB in the VLF signal strength at the time of maximum solar obscuration (84% at 01:53 UT) as compared to those observed on the control days. Estimated values of change in Wait ionospheric parameters: reflection height (h′) in km and inverse scale height parameter (β) in km−1 from Long Wave Propagation Capability (LWPC) model during the maximum eclipse phase as compared to unperturbed ionosphere are 7 km and 0.055 km−1, respectively. Moreover, the D-region electron density estimated from model computation shows 95% depletion in electron density at the height of ∼71 km. The reflection height is found to increase by ∼7 km in the D-region during the eclipse as compared to those on the control days, implying a depletion in the Lyman-α flux by a factor of ∼7. The present observations are discussed in the light of current understanding on the solar eclipse induced D-region dynamics. 相似文献
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WIND飞船在2010年11月15日观测到两个临近的脉冲型太阳能量电子事件, 这两个事件在1AU处呈现出不同类型的通量-时间曲线. 事件一的通量表现出快速上升及快速下降的特性; 事件二则表现为缓慢上升, 更缓慢下降, 事件二的持续时间是事件一的5~17倍. 以往的解释认为事 件二中的电子在行星际受到了更强的散射. 本文引入等腰三角形的释放函数并 求解电报方程, 利用得到的解对1AU处的观测进行拟合. 根据最佳拟合结果 反推两事件在太阳上的释放函数和在行星际传播的平均自由程, 发现造成两事 件在1AU处能谱和通量-时间曲线形状不同的原因是太阳上电子 加速过程的不同而非行星际散射. 结合SOHO卫星的白光观测, 发现两事件可能 与一个CME (日冕物质抛射)相关, 并进一步推测了这两个太阳电子事件可能 的加速图像. 相似文献
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J. Šafránková Z. Němeček L. Přech A. Koval I. Čermák M. Beránek G. Zastenker N. Shevyrev L. Chesalin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(1):153-159
The monitoring of solar wind parameters is a key problem of the space weather program. We are presenting a new solution of plasma parameter determination suitable for small and fast solar wind monitors. The first version will be launched during the SPECTR-R project into a highly elongated orbit with apogee ∼350,000 km. The method is based on simultaneous measurements of the total ion flux and ion integral energy spectrum by six identical Faraday cups. Three of them are dedicated to determination of the ion flow direction, the other three (equipped with control grids supplied by a retarding potential) are used for determination of the density, temperature, and speed of the plasma flow. The version under development is primarily designed for the measurements in the solar wind and tail magnetosheath, thus for velocities range from 270 to 750 km/s, temperatures from 1 to 30 eV, and densities up to 200 cm−3. However, the instrument design can be simply modified for measurements in other regions with a substantial portion of low-energy plasma as a subsolar magnetosheath, cusp or low-latitude boundary layer. Testing of the engineering model shows that the proposed method can provide reliable plasma parameters with a high time resolution (up to 8 Hz). The paper presents not only the method and its technical realization but it documents all advantages and peculiarities of the suggested approach. 相似文献