Conjugate observations of flow diversion in the magnetotail and auroral arc extension in the ionosphere
Conjugate observations of flow diversion in the magnetotail and auroral arc extension in the ionosphere
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DOI：
10.1002/jgra.50419
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发表时间：
2013-08
期刊：
影响因子：
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通讯作者：
Z. Yao;V. Angelopoulos;Z. Pu;S. Fu;M. Kubyshkina;J. Liu;X. Chu;T. Nishimura;X. Cao
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文献类型：
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作者：
Z. Yao;V. Angelopoulos;Z. Pu;S. Fu;M. Kubyshkina;J. Liu;X. Chu;T. Nishimura;X. Cao
我们给出了一个内磁层等离子体流转移事件的案例研究，以说明2008年1月29日THEMIS卫星和全天成像仪(ASIS)共轭观测期间近地压力演变、场向电流(FAC)产生和相关极光演变的影响。在0831UT，在X~18Re的THC观测到一股向地面的流动，这可能与ASI站FSMI观测到的极光流光有关。近地卫星THD和THd在Y方向上被~1Re隔开，并以磁性映射到先前存在的极光弧上，也观测到了向地球的流动，但在磁尾和电离层之间的Alfvén渡越时间很小，约为20 S。当地球上的水流到达THD和THD时，极光弧线靠近THD和明亮的脚印。在THD和赤道磁尾之间形成的黄昏气压梯度，对应于向上的FAC，与极光亮化相一致。0834UT时，首先在THD观察到气流向东转移，然后在THD进一步向东转移。在这股气流的头部，观测到了与THD相一致的气压变化，并以约400公里/S的速度向东传播，这与在THD和THD足迹附近向东的极光扩张是一致的。磁场的By分量的同时扰动表示在两个航天器位置的FAC对向东运动。我们将压力变化解释为观察到的FAC的生成器，该FAC为电弧及其向东扩展提供了支持。
We present a case study of a plasma flow diversion event in the inner magnetosphere to illustrate the effects of near‐Earth pressure evolution, field‐aligned current (FAC) generation, and associated auroral evolution during conjugate observations from THEMIS satellites and All‐Sky Imagers (ASIs) on 29 January 2008. At ~0831 UT, an earthward flow at THC, at X ~ 18 Re, was observed which was likely to be associated with an auroral streamer observed at the ASI station FSMI. Near‐Earth satellites THD and THE, separated in the Y‐direction by ~1 Re, and magnetically mapping onto the preexisting aurora arc, also observed the earthward flow but with a small Alfvén transit time of ~20 s between the magnetotail and the ionosphere. As the earthward flow arrived at THD and THE, the aurora arc near the footprints of THD and THE brightened. A duskward pressure gradient developed between THD and THE in the equatorial magnetotail, corresponding to an upward FAC and consistent with the auroral brightening. At ~0834 UT, an eastward diversion of the flow was observed first at THE and later at THD, further to the East. At the head of that flow, pressure variations, coherent between THE and THD, were observed to propagate Eastward at ~400 km/s, consistent with an eastward auroral expansion near the footprints of THE and THD. Concurrent perturbations of the By component of the magnetic field signify eastward motion of a FAC pair at the two spacecraft locations. We interpret the pressure variations as the generator of the observed FAC that feeds the arc and its eastward expansion.