Radar observations of auroral zone flows during a multiple-onset substorm
Radar observations of auroral zone flows during a multiple-onset substorm
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多发亚暴期间极光区流的雷达观测
DOI：
10.1007/s00585-995-1144-2
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发表时间：
1995
影响因子：
1.9
通讯作者：
T. Yeoman
中科院分区：
文献类型：
--
作者：
J. P. Morelli;R. Bunting;S. Cowley;Charles J. Farrugia;Charles J. Farrugia;M. Freeman;E. Friis;G.O.L. Jones;G.O.L. Jones;Mark Lester;R. V. Lewis;R. V. Lewis;Hermann Lühr;D. Orr;M. Pinnock;Geoff D. Reeves;P. Williams;T. Yeoman
本文分析了1988年4月12日一次多次爆发的亚暴期间的地面磁场、电离层流、地球同步粒子和行星际资料。我们的主要结果涉及电离层流动的调制过程中发生的脉冲电射流激活与每个发病。在扰动的第一个小时里，这些每隔12.5分钟发生一次，并涉及在午夜前扇区形成一个新的强烈的向西电流丝，就在大规模流动驱动的先前存在的扩展电流系统的极向。这些细丝是\sim 1 h MLT宽（\sim 600 km），最初向极地扩展到\sim 300 km的宽度，然后向赤道收缩并与先前存在的电流合并，通常使后者在幅度上增强和/或在纬度上扩展。在脉冲电射流中，在最初的几分钟内，流动被抑制到50-100 m s-1或更小，然后在快速合并阶段以0.5-1.0 km s-1的速度向赤道方向涌动。这意味着，在脉冲电射流内的沉淀诱导的霍尔电导率最初上升到超过\sim100毫欧，然后在几分钟内衰减。这个值相比，霍尔电导率\sim20毫欧的准稳态电流区域，和几个毫欧或更少的区域poleward的电射流和在发病前的电离层。初步的证据也被发现，流涌传播从午夜到早晨部门，在那里他们与逮捕赤道运动或极向收缩的电流系统。这些意见进行了讨论，目前的理论范式的全球行为的领域和流动发生在亚暴。
We present an analysis of ground magnetic field, ionospheric flow, geosynchronous particle, and interplanetary data during a multiple-onset substorm on 12 April 1988. Our principal results concern the modulations of the ionospheric flow which occur during the impulsive electrojet activations associated with each onset. During the first hour of the disturbance these take place every \sim12.5 min and involve the formation of a new intense westward current filament in the premidnight sector, just poleward of the preexisting extended current system driven by the large-scale flow. These filaments are \sim1 h MLT wide (\sim600 km), and initially expand poleward to a width of \sim300 km before contracting equatorward and coalescing with the preexisting current, generally leaving the latter enhanced in magnitude and/or expanded in latitude. Within the impulsive electrojets the flow is found to be suppressed to values 50–100 m s−1 or less during the first few minutes, before surging equatorward at 0.5-1.0 km s−1 during the phase of rapid coalescence. The implication is that the precipitation-induced Hall conductivity within the impulsive electrojet initially rises to exceed \sim100 mho, before decaying over a few minutes. This value compares with Hall conductivities of \sim20 mho in the quasi-steady current regions, and a few mho or less in the regions poleward of the electrojets and in the preonset ionosphere. Preliminary evidence has also been found that the flow surges propagate from midnight to the morning sector where they are associated with arrested equatorward motion or poleward contractions of the current system. These observations are discussed in terms of present theoretical paradigms of the global behaviour of fields and flows which occur during substorms.