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Simultaneous energetic particle and magnetic field observations from the GEOTAIL spacecraft in the distant tail (XGSM -150 Re) have been analysed to study the response of the Earths magnetotail during a strong substorm (AE 680 nT). At geosynchronous altitude, LANL spacecraft recorded three electron injections between 0030 UT and 0130 UT, which correspond to onsets observed on the ground at Kiruna Ground Observatory. The Earths magnetotail responded to this substorm with the ejection of five plasmoids, whose size decreases from one plasmoid to the next. Since the type of magnetic structure detected by a spacecraft residing the lobes, depends on the Z extent of the structure passing underneath the spacecraft, GEOTAIL is first engulfed by a plasmoid structure; six minutes later it detects a boundary layer plasmoid (BLP) and finally at the recovery phase of the substorm GEOTAIL observes three travelling compression regions (TCRs). The time-of-flight (TOF) speed of these magnetic structures was estimated to range between 510 km/s and 620 km/s. The length of these individual plasmoids was calculated to be between 28 Re and 56 Re. The principal axis analysis performed on the magnetic field during the TCR encountered, has confirmed that GEOTAIL observed a 2-D perturbation in the X-Z plane due to the passage of a plasmoid underneath. The first large plasmoid that engulfed GEOTAIL was much more complicated in nature probably due to the external, variable draped field lines associated with high beta plasma sheet and the PSBL flux tubes surrounding the plasmoid. From the analysis of the energetic particle angular distribution, evidence was found that ions were accelerated from the distant X-line at the onset of the burst associated with the first magnetic structure. 相似文献
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用单流体和双流体ＭＨＤ近似，研究了近磁尾位形不稳定性（ＮＥＴＣ）．分析表明，ＮＥＴＣ可能存在两种漂移不稳定情况Ｃ１和Ｃ２与卫星观测资料对比显示，Ｃ２较容易在亚暴膨胀相前夕出现，它可以解释亚暴膨胀相期间磁场和等离子体扰动的特征周期、尾向传播速度、磁场扰动和等离子体压强扰动之间的位相关系，场向电流的周期性结构，西向涌浪头部的电子沉降和极光隆起等观测特性和现象．薄电流片的极端情况（Ｒｃ≈ｒｉ）不在本文的讨论范围之内． 相似文献
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I. Sandahl S. Barabash H. Borg E. Y. Budnik E. M. Dubinin U. Eklund H. Koskinen K. Lundin R. Lundin A. Mälkki R. Pellinen N. F. Pissarenko T. Pulkkinen A. V. Zakharov 《Annales Geophysicae》1999,17(5):659-673
The PROMICS-3 instrument on Interball-2 is nominally identical to the PROMICS-3 instrument on Interball-1. It performs three-dimensional measurements of ions in the energy range 4 eV–70 keV with mass separation and of electrons in the energy range 300 eV–35 keV. Interball-2 was launched on August 29, 1996, into an orbit with the same inclination as that of Interball-1, 63°, but with apogee at 20 000 km. In this study the PROMICS-3 instrument on Interball-2 is briefly described and examples of the first results are presented. Firstly, we report observations of upward moving molecular ions with energies of up to 700 eV at the poleward edge of the auroral oval. Previous observations of outflowing molecular ions have been at lower altitudes and lower energies. Secondly, we show observations of dawnside magnetosheath plasma injections. Using conjugate data from both PROMICS-3 instruments we have found dispersion structures above the morningside auroral oval, which occurred simultaneously with isolated “pockets” of magnetosheath plasma at a distance of XGSM = −14 to −12 RE, which had been injected into the inner part of the low-latitude boundary layer. These isolated plasma structures were sites of strong field-aligned currents and are proposed to be the magnetospheric counterparts of the dispersion structures. 相似文献
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Magnetospheric substorms represent the basic dynamic process in the coupled solar wind -- magnetosphere -- ionosphere system. Recent satellite missions have considerably advanced our means to monitor this vast environment. These observations are interpreted in the context of a hierarchy of models: Global MHD simulations and various techniques of nonlinear physics are used to characterize the large-scale features, whereas microphysical models are used to study the small-scale processes. Empirical models are described in order to address questions that involve meso-scale or multi-scale phenomena. We discuss some of the recent observations and relate those to new advancements in various modeling techniques. 相似文献
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O. Verkhoglyadova A. Agapitov A. Andrushchenko V. Ivchenko S. Romanov Yu. Yermolaev 《Annales Geophysicae》1999,17(9):1145-1154
Compressional waves with periods greater than 2 min (about 10–30 min) at low geomagnetic latitudes, namely compressional Pc5 waves, are studied. The data set obtained with magnetometer MIF-M and plasma analyzer instrument CORALL on board the Interball-1 are analyzed. Measurements performed in October 1995 and October 1996 in the dawn plasma sheet at −30 RE ≤ XGSM and |ZGSM| ≤ 10 RE are considered. Anti-phase variations of magnetic field and ion plasma pressures are analyzed by searching for morphological similarities in the two time series. It is found that longitudinal and transverse magnetic field variations with respect to the background magnetic field are of the same order of magnitude. Plasma velocities are processed for each time period of the local dissimilarity in the pressure time series. VeloCity disturbances occur mainly transversely to the local field line. The data reveal the rotation of the veloCity vector. Because of the field line curvature, there is no fixed position of the rotational plane in the space. These vortices are localized in the regions of anti-phase variations of the magnetic field and plasma pressures, and the vortical flows are associated with the compressional Pc5 wave process. A theoretical model is proposed to explain the main features of the nonlinear wave processes. Our main goal is to study coupling of drift Alfven wave and magnetosonic wave in a warm inhomogeneous plasma. A vortex is the partial solution of the set of the equations when the compression is neglected. A compression effect gives rise to a nonlinear soliton-like solution. 相似文献
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本文通过利用包含离心力的自洽、轴对称稳态木星磁层模型,以及等离子体细丝运动理论对磁尾重联产生的磁通量管向内输运进行研究.基于细丝运动理论模型,通过MHD数值模拟我们可以得到磁通量管随时间变化的许多特性.模拟结果表明,重联产生的磁通量管向内运动可到达10RJ以内,磁通量管赤道部分的速度可以达到350km·s-1左右,表现出很强的向行星方向的流动.初始磁通量管中的等离子体密度和压强均小于周围介质,随着它迅速向木星方向运动,它的等离子体密度由于体积压缩逐渐上升,等离子体压强则逐渐上升到与周围介质相当.磁通量管在电离层上足点向赤道方向的运动滞后于它在赤道面上向行星方向的运动. 相似文献
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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
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D. V. Sarafopoulos M. A. Athanasiu E. T. Sarris T. Yamamoto S. Kokubun 《Annales Geophysicae》1999,17(9):1121-1133
We study an interval of 56 h on January 16 to 18, 1995, during which the GEOTAIL spacecraft traversed the duskside magnetosheath from X ≅ −15 to −40 RE and the EPIC/ICS and EPIC/STICS sensors sporadically detected tens of energetic particle bursts. This interval coincides with the expansion and growth of a great geomagnetic storm. The flux bursts are strongly dependent on the magnetic field orientation. They switch on whenever the Bz component approaches zero (Bz ≅ 0 nT). We strongly suggest a magnetospheric origin for the energetic ions and electrons streaming along these “exodus channels”. The time profiles for energetic protons and “tracer” O+ ions are nearly identical, which suggests a common source. We suggest that the particles leak out of the magnetosphere all the time and that when the magnetosheath magnetic field connects the spacecraft to the magnetotail, they stream away to be observed by the GEOTAIL sensors. The energetic electron fluxes are not observed as commonly as the ions, indicating that their source is more limited in extent. In one case study the magnetosheath magnetic field lines are draped around the magnetopause within the YZ plane and a dispersed structure for peak fluxes of different species is detected and interpreted as evidence for energetic electrons leaking out from the dawn LLBL and then being channelled along the draped magnetic field lines over the magnetopause. Protons leak from the equatorial dusk LLBL and this spatial differentiation between electron and proton sources results in the observed dispersion. A gradient of energetic proton intensities toward the ZGSM= 0 plane is inferred. There is a permanent layer of energetic particles adjacent to the magnetosheath during this interval in which the dominant component of the magnetic field was Bz. 相似文献
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