共查询到18条相似文献，搜索用时 93 毫秒
1.
本文利用星簇Cluster的三颗卫星(C1,C3和C4)在2001年和2002年的数据,研究了快速对流事件（RCE， Rapid Convection Event）及其与亚暴的关系.结果显示单点卫星对RCE的观测,不能反映磁尾RCE的真实情况.在2002年7月25日发生的一次RCE事件, C1和C3观测到这次RCE，C4却没有观测到.在三颗卫星联合观测到的306次RCE中,C1观测到215次,C3观测到266次,C4观测到227次.统计研究表明，单点卫星观测到的RCE的平均时间也不能准确反映磁层内的RCE.由此推论在整个中心等离子体片内,快速对流事件所承担的能量和磁通量的输运量,可能远大于单点卫星观测给出的结果.用速度来定义的磁尾爆发性整体流(BBF，Bursty Bulk Flow)与亚暴的关系,比用磁通量定义的RCE与亚暴的关系要更加紧密. 相似文献
2.
本文主要应用THEMIS卫星的磁场和等离子体流观测数据,分析了2008年1月5日08∶51~08∶57 UT亚暴膨胀相期间磁尾的一个近地重联事件.在亚暴膨胀相期间,地面的全天空成像仪清楚地记录到了极光的极向扩展,THEMIS的P5卫星在地球同步轨道附近观测到了磁场的偶极化现象.在亚暴膨胀相末期的08∶51~08∶57 UT期间,P3(XGSM~-9.12RE) 和P4 (XGSM ~-9.40RE) 同时观测到了一对方向相反的高速等离子体流.这对方向相反的高速等离子体流是由磁尾的重联现象所引起.重联的位置被估计位于XGSM ~-9.12RE 和XGSM~-9.40RE之间较小的空间范围内.并且,在重联位置的两侧,重联的Hall效应被P3和P4两颗卫星观测到.因此,这一磁尾重联事件发生在距离地球非常近的空间范围内. 相似文献
3.
本文根据OMNI、TC-2卫星、LANL系列卫星、Cluster星簇卫星(C1-C4)以及加拿大的8个中高纬地磁台站的观测数据,研究了2005年8月24日强磁暴(SYM-Hmin~ -179 nT)主相期间的强亚暴(ALmin~ -4046 nT)事件特征.该强磁暴在大振幅(IMF Bz min~ -55.57 nT)、短持续时间(~90 min)的行星际磁场条件下产生,有明显的磁暴急始(SSC),强度较大且持续时间较短.发生在磁暴主相期间的亚暴发展的主要特征如下:亚暴增长相期间,C1-C4卫星先后穿越中心等离子体片;亚暴膨胀相触发后,在近地磁尾(X~-6RE)可观测到磁场偶极化现象;等离子体无色散注入区在亚暴onset开始后迅速沿经向扩展,但被限制在有限的经度范围;磁纬60°附近,Pi2地磁脉动振幅超过了100 nT.膨胀相开始后,在中、高磁纬地磁台站可观测到负湾扰,近地磁尾可观测到Pi2空间脉动,中磁尾区域可观测到尾向流、磁重联以及O+/H+数密度比值在亚暴onset之后增大等现象.分析表明该强磁暴主相期间的强亚暴现象发生时序是自内向外:X~-6RE处TC-2观测到磁场偶极化(~09:42:30 UT),同步轨道卫星LANL1994-084观测到等离子体无色散注入(~09:44:30 UT),X~-17.8RE处C1观测到磁场重联(~09:45:30 UT),由此推断该亚暴事件很可能是近地磁尾不稳定性触发产生,其发生区域距离地球很近. 相似文献
4.
亚极光区极化流（Subauroral Polarization Streams, SAPS）为快速流动的西向等离子体流,位于昏侧-子夜前亚极光区,是磁层-电离层-热层耦合的重要过程之一.本文利用密西根大学的RAM （Ring current-Atmosphere Interaction Model）模型对一次典型磁暴期间发生的SAPS事件进行了模拟,并与DMSP卫星观测值进行了比较.结果表明：模拟结果能大致反映观测现象;模拟得到的SAPS峰值速度所在纬度随磁暴时间的变化与观测值有较大差别;SAPS速度观测值在约18∶00 UT和约20∶00 UT左右出现两个峰值,而模拟值只有一个峰值,出现在约18∶00 UT,主要原因是模型对亚暴过程的模拟存在不足. 相似文献
5.
亚暴期间磁尾等离子体片离子注入内磁层能够激发电磁离子回旋(EMIC)波.对应于这种EMIC波,地面磁力仪可观测到周期逐渐减小的地磁脉动(IPDP).利用GOES卫星数据,地磁指数和加拿大CARISMA地磁台站的数据,我们研究了IPDP事件的产生与亚暴磁尾注入的关系.同时利用CARISMA地磁台链中的MCMU和MSTK两个台站,从2005年4月到2014年5月期间的观测数据,统计分析了亚暴期间的IPDP事件,研究了IPDP事件的出现率关于季节和磁地方时的分布特征.我们总共获得128个两个台站同时观测的IPDP事件.该类事件关于季节分布的发生率,冬季最小,为13.28%,春季最大,为32.81%,结果表明IPDP事件关于季节分布的发生率受到电离层电导率及亚暴发生率的影响.两个台站同时观测到的IPDP事件最大出现率出现在15—18 MLT(磁地方时),结果表明IPDP事件主要由亚暴期间产生的能量离子注入内磁层,西向漂移遇到等离子体层羽状结构(Plume)区的高密度等离子体所激发. 相似文献
6.
本文利用星簇CLUSTER的三颗卫星数据分析了磁宁静期磁尾爆发性整体流（BBFs, Bursty Bulk Flows）的时间尺度, 并与单个卫星的结果做了比较. 事例研究表明, 利用三颗卫星观测数据判断的BBFs的时间尺度比单个卫星的大一倍左右. 对于三颗卫星观测到的同一个BBFs, BBFs在晨昏方向上的摆动决定了CLUSTER的三个卫星观测到BBFs的先后次序. 三颗卫星的观测也显示了BBFs的高度局域化特征. 磁宁静期磁尾BBFs寿命的增大, 使得BBFs携带的质量和能量的地向输运增加. 这种地向输运增加的结果是: 磁尾储存的能量得到较为平稳的释放, 改变了亚暴起始产生的时间, 为解决磁层压力平衡矛盾（PBI, Pressure Balance Inconsistency）问题提供了新的思路. 相似文献
7.
本文研究了2005年8月24日强磁暴（事件A,Dst〈-200nT,AE指数平均值为436nT）与2006年10月28日弱磁暴（事件B,Dst〉-50nT,AE指数平均值为320nT）期间同步轨道高能电子通量的演化过程．LANL和GOES-12卫星观测数据表明：恢复相期间,事件A和事件B中高能电子通量均上升约10倍;随着亚暴持续的发生,Cluster C4卫星均观测到同步轨道存在强烈的哨声波合声模（波强达到10^-5nT^2／Hz）,波幅主要依赖于亚暴AE指数,与Dst指数关联较弱．采用高斯波谱拟合,求解了控制波粒相互作用的Fokker-Planck扩散方程．模拟结果表明：两例事件中的合声模能有效加速1MeV左右的高能电子,且在高投掷角区域加速作用更加明显;加速时间尺度和幅度与观测数据基本吻合．本文研究为合声模加速辐射带高能电子过程提供了新的观测支持． 相似文献
8.
在磁静和亚暴期间,TC 1卫星在近地磁尾，包括晨昏两侧和夜侧的尾瓣、等离子体片边界层和等离子体片区域都观测到大量来自电离层的尾向流事件.尾向流在赤道面附近最强，在夜侧较晨昏两侧强；尾向流有从晨昏两侧向夜侧运动的趋势；尾向流随距地球距离增加而逐渐增强.与来自中磁尾的地向流相比，近地磁尾近赤道区域来自电离层的尾向流具有低温高密特性.2004年7月1日至2004年10月31日期间TC 1卫星在近地磁尾（7RE～13RE之间，RE为地球半径）观测到持续时间超过3 min的尾向流共516起.对这516起尾向流的统计研究结果显示：（1）尾向流在从等离子体片边界层向等离子体片的运动过程中流速会逐渐减弱、密度逐渐增高，温度有逐渐下降的趋势；（2）对尾向流平行温度和垂直温度的分析显示不同等离子体区域的尾向流都有较明显的各向异性；（3）在从等离子体片边界层向等离子体片的运动过程中，尾向流逐渐趋向各向同性. 相似文献
9.
GEOTAIL卫星于1994年1月15日亚暴期间，在深磁尾（x＝96RE）观测到多重等离子体团及与之相对应的高能离子爆，作者以宁静磁尾平衡位形为初态，考虑介质的可压缩性，数值研究亚暴期间磁尾动力学过程．计算结果展现了等离子体团间歇性形成及其运动发展过程．体现了强亚暴事件中储存于碰尾的能量，通过多重等离子体团的排放而逐渐释放的进程．数值结果还表明：持续施加于边界上的晨昏电场及由此引发的驱动重联是导致等离子体团准周期形成的主要因素．此外，作者还考察尾瓣内任一点磁场强度及其分量随时间的演化，它与行进压缩区（TCRs）的观测特征基本相符． 相似文献
10.
磁层亚暴的发生与近磁尾（约6～8 RE）电流片中断和中磁尾（约20～30 RE）磁场重联密切相关,而极光的极向扩展、电流片中断和磁尾重联的时序过程对于认识亚暴的触发机制至关重要. 本文利用位于中磁尾的CLUSTER卫星,同步轨道附近LANL-01、LANL-97卫星,近磁尾POLAR和 极区IMAGE卫星的观测,分析了单个亚暴事例.结果表明,在此事件中,中磁尾磁场重联起始比近尾电流片中断早3 min发生,电流片中断发生4 min后,IMAGE卫星观测到极光增亮,同时AE指数突然增大,亚暴膨胀相起始. 观测结果与亚暴中性线模型较为吻合. 相似文献
11.
V. A. Parkhomov N. L. Borodkova A. V. Dmitriev P. M. Klimov R. A. Rakhmatulin 《Geomagnetism and Aeronomy》2011,51(7):979-993
By the example of commencement and development of two successive substorms on August 1, 1998, the mechanism resulting in the
initiation of auroral processes (substorms) is discussed. These events were chosen due to the favorable position of satellites
in the solar wind, magnetosphere, and plasma sheet, as well as due to the availability of satellite and ground-based observation
data. 相似文献
12.
《Journal of Atmospheric and Solar》2000,62(10):817-824
A broad outline is presented of what has been learned over the past decade concerning magnetosphere–ionosphere (M-I) coupling, dynamic interchanges of particles and electromagnetic energy between magnetically conjugate regions of near-Earth space. Although the concept of M-I coupling is useful for relating characteristics of distant source regions to ionospheric signatures, it is fundamentally incomplete, and must include connections to the interplanetary medium. With single satellite missions “we’ve gone about as far as we can go”. Ground-based magnetometer, optical and/or radar measurements are now routinely integrated with complementary data acquired by satellites to interpret electrodynamic signatures. Simultaneous measurements in the ionosphere and magnetosphere show that Alfvén waves at Pi 2 frequencies are important sources of M-I coupling near times of substorm onsets. The same measurements suggest that the braking of bursty bulk flow (BBF) structures is not important for triggering substorms. M-I coupling signatures of BBFs in the nightside ionosphere are compared with those of flux transfer and impulsive penetration events on the dayside. We then explore some implications of the hypothesis that BBF plasma is initially accelerated near the equatorial plane. Subsequent braking would result from electrodynamic coupling which redistributes energy and momentum to plasma in the high latitude parts of flux tubes and in the ionosphere. 相似文献
13.
N. G. Kleimenova M. Kubicki A. Odzimek L. M. Malysheva L. I. Gromova 《Geomagnetism and Aeronomy》2017,57(3):266-273
We have studied the influence of daytime polar substorms (geomagnetic bays under the IMF Bz > 0) on variations of the vertical gradient of the atmospheric electric field potential (Ez) observed at the Polish Hornsund Station (Svalbard, Norway). Only the observations of Ez under “fair weather” conditions were used, i.e. in the absence of strong wind, precipitations, low cloud cover, etc. We studied more than 20 events of daytime polar substorms registered by the Scandinavian chain of IMAGE magnetometers in 2010–2014 during the “fair weather” periods at the Hornsund Station. Analysis of the observations showed that Ez significantly deviates from the its background variations during daytime, as a rule, when the Hornsund Station is in the region of projection of the daytime auroral oval, the position of which was determined from OVATION data. It was shown that the development of a daytime polar substorm leads to fluctuating enhance of Ez values. It was found that Ez surges are accompanied by intensification of field-aligned electric currents outflowing from the ionosphere, which were calculated from the data of low-orbit communication satellites of the AMPERE project. 相似文献
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15.
本文用多步隐格式方法,求解包含电阻的磁流体力学方程组,对磁层亚暴扩展相作数值模拟.计算结果展现了亚暴扩展相期间磁尾变化的主要特征.它表明,球向和尾向等离子体流与准稳态重联有关.等离子体团的尾向喷发,致使中性线尾侧电流片内的密度降低,等离子体片变薄.中性线近地侧的等离子体团朝着地球运动,并合并于地球附近的重联区内. 相似文献
16.
N. G. Kleimenova E. E. Antonova O. V. Kozyreva L. M. Malysheva T. A. Kornilova I. A. Kornilov 《Geomagnetism and Aeronomy》2012,52(6):746-754
A new type of high-latitude magnetic bays is revealed at geomagnetic latitudes higher than 71°, called ??polar substorms.?? It is shown that polar substorms differ from both classical substorms and high-latitude geomagnetic disturbances of the type of polar boundary intensifications (PBIs). While classical substorms start at latitudes below 67° and then expand poleward, polar substorms start almost simultaneously in the evening-night polar region of the oval. In contrast to PBIs, accompanied by auroral streamers expanding southward, polar substorms are accompanied by auroral arcs quickly traveling northward. It is shown that polar substorms are observed before midnight (20?C22 MLT) under weak geomagnetic activity (Kp ?? 2) during the late recovery phase of a magnetic storm. It is shown that a typical feature of polar substorms is the simultaneous excitation of highly intensive Pi2 and Pi3 geomagnetic pulsations at high latitudes, which exceed the typical amplitude of these pulsations at auroral latitudes by more than an order of magnitude. The duration of pulsations is determined by the substorm duration, and their amplitude decreases sharply at geomagnetic latitudes below ??71°. It is suggested that pulsations reflect fluctuations in ionospheric currents connected with polar substorms. 相似文献
17.
M. Stepanova T. Vucina-Parga E. Antonova I. Ovchinnikov Y. Yermolaev 《Journal of Atmospheric and Solar》2005,67(17-18):1815
Fluctuations of the plasma bulk velocity across the plasma sheet are studied using single-point measurements from the Corall instrument on board the Interball/Tail satellite. Several hour-long intervals of continuous data corresponding to quiet geomagnetic conditions and different phases of isolated substorms are analyzed. The plasma sheet flow appears to be strongly turbulent, i.e. dominated by fluctuations that are unpredictable. Corresponding eddy diffusion coefficients were obtained as a function of the autocorrelation time and rms velocity of the fluctuations. It was found that the amplitude of the turbulence and the values of eddy-diffusion coefficients increase significantly during substorm growth and expansion phases and they decrease to their initial level during the recovery phase. We also studied a relationship between the eddy-diffusion coefficients and the absolute value of the geomagnetic field, also measured by the Interball/Tail satellite. It was found that this relationship varies depending on the phase of substorm, indicating possible change in the turbulence regimen with substorm phase. 相似文献
18.
K. Kauristie M. V. Uspensky N. G. Kleimenova O. V. Kozyreva S. V. Dubyagin A. A. Vlasov 《Geomagnetism and Aeronomy》2013,53(5):613-625
The analysis results of a complex of phenomena that were developing in the evening and morning magnetospheric and ionospheric sectors during two events (January 18 and February 19, 2008) are presented. The analysis is based on the observation data in the magnetotail from the THEMIS satellites and ground-based observations in the morning (MIRACLE network) and nighttime (THEMIS ground-based network) sectors. The events with moderate substorms in the nighttime sector were preceded by strong geomagnetic Pc5 pulsations in the morning sector, the regime of which changed during the development of auroral disturbances. The substorms were accompanied by dipolizations in the magnetotail at distances of ~10 Re and unexpected jump-like fluxes of ～200-keV electrons. The fluxes appeared within several minutes after a breakup at three central THEMIS satellites simultaneously spaced up to 1.7 Re. According with the ASC data at the NAL observatory (3 frames/min) and with the THEMIS network of ASC data, onset of auroral activations in the night and morning sectors occurred simultaneously. Probable reasons for the sudden suppression or intensification of Pc5 pulsations are discussed. 相似文献