Dynamics of the inner magnetosphere near times of substorm onsets
Dynamics of the inner magnetosphere near times of substorm onsets
复制标题
亚暴爆发附近内磁层的动态
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
F. Mozer
中科院分区：
文献类型：
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作者：
N. Maynard;W. J. Burke;E. Basinska;G. Erickson;W. Hughes;H. Singer;A. Yahnin;D. Hardy;F. Mozer
利用CRRES对磁场和电场、高能电子通量的测量，结合地面观测，研究了亚暴发生前后内磁层的电动力学。六个事件进行了详细研究，跨越2100至0000 MLT部门和L值从5到7。在每种情况下，黎明-黄昏电场增强了典型的背景电场，并观察到显着的低频脉动活动。脉动的幅度大于背景电场。交叉尾电场的黄昏-黎明偏移通常与CRRES的电流和粒子能量变化以及地面上观察到的ULF波活动相关。电场和坡印廷矢量的变化与周期在Pi 2范围内是一致的反弹阿尔芬波，提供电离层和等离子体片之间的电磁通信。在三次轨道运行期间观测到远离电离层的磁场排列电流细丝的磁特征，据推测这与亚暴电流楔有关。在所有情况下，地面签名的亚暴膨胀观察到至少5分钟前，在CRRES的电子注入。三次注射后，检测到逆流，低能电子的场向通量。我们开发了一个经验的亚暴发生的情况。该过程的增长，从波纹的等离子体片的内边缘与黄昏的电场的漂移，开始之前的偶极。来自向内等离子体对流的制动的能量以坡印亭通量的形式流入电离层。磁层-电离层耦合中，波印廷通量的反射起着至关重要的作用。亚暴发展时，显着的能量（正反馈？）在两个方向流动，第二个周期比第一个周期更强。当两个方向上的能量流都很弱时（负反馈？）“爆炸性增长阶段”的特征发生在亚暴爆发后，即亚暴扩张阶段的早期。在电磁能量流离开电离层期间或结束时，加热的电子到达航天器，而对流是朝向地球的。
The electrodynamics of the inner magnetosphere near times of substorm onsets have been investigated using CRRES measurements of magnetic and electric fields, energetic electron fluxes, in conjunction with ground-based observations. Six events were studied in detail, spanning the 2100 to 0000 MLT sector and L values from 5 to 7. In each case the dawn-dusk electric field was enhanced over typical background electric fields, and significant, low-frequency pulsation activity was observed. The amplitudes of the pulsations were larger than the background electric fields. Dusk-dawn excursions of the cross-tail electric field often correlated with changes in currents and particle energies at CRRES and with ULF wave activity observed on the ground. Variations of the electric field and Poynting vectors with periods in the Pi 2 range are consistent with bouncing AlfVen waves that provide electromagnetic communication between the ionosphere and plasma sheet. Magnetic signatures of field-aligned current filaments directed away from the ionosphere, presumably associated with the substorm current wedge, were observed during three orbits. In all cases, ground signatures of substorm expansion were observed at least 5 min before the injection of electrons at CRRES. Field-aligned fluxes of counter-streaming, low-energy electrons were detected after three of the injections. We develop an empirical scenario for substorm onset. The process grows from ripples at the inner edge of the plasma sheet associated with dusk-dawn excursions of the electric field, prior to the beginning of dipolarization. Energy derived from the braking of the inward plasma convection flows into the ionosphere in the form of Poynting flux. Subsequently reflected Poynting flux plays a crucial role in the magnetosphere-ionosphere coupling. Substorms develop when significant energy (positive feedback?) flows in both directions, with the second cycle stronger than the initial. Pseudobreakups occur when energy flow in both directions is weak (negative feedback?). “Explosive-growth-phase” signatures occur after onset, early in the substorm expansion phase. Heated electrons arrive at the spacecraft while convection is earthward, during or at the end of electromagnetic energy flow away from the ionosphere.