How Much Flux Does a Flux Transfer Event Transfer?
How Much Flux Does a Flux Transfer Event Transfer?
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DOI：
10.1002/2017ja024730
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发表时间：
2016-12
期刊：
影响因子：
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通讯作者：
R. Fear;L. Trenchi;J. Coxon;S. Milan
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文献类型：
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作者：
R. Fear;L. Trenchi;J. Coxon;S. Milan
通量转移事件是向阳面磁层顶重联的爆发，它引起一系列磁层/电离层仪器观测到的特征信号。一个突出的问题是，空间和电离层对每个通量转移事件所打开的通量的估计之间存在根本的不匹配-换句话说，它们在邓吉循环中的整体意义。基于航天器对单个通量传输事件（FTE）的通量含量的估计对应于每个事件传输的通量相当于磁层中开放通量的约1%，而基于全球尺度雷达和极光观测的研究表明，这个数字可能是10%。在前一种情况下，通量转移事件将是邓吉循环中的一个次要细节，但在后一种情况下，它们可能是其主要驱动力。我们提出了两个连接的观测通量传输事件观察到的集群航天器和脉冲电离层流动观察到的超级双极光雷达网络（SuperDARN）网络。在这两种情况下，Cluster和其中一个SuperDARN雷达观测到了类似数量的FTE特征，但航天器和电离层观测的方位角分离不同（即，航天器与尖点喉部的距离）。我们认为，现有的通量估计不匹配的原因是由于对FTE结构的隐含假设，默认忽略了大部分的通量打开的机制，基于较长的重联线。如果考虑这些机制的影响，则发现更好的匹配。
Flux transfer events are bursts of reconnection at the dayside magnetopause, which give rise to characteristic signatures observed by a range of magnetospheric/ionospheric instrumentation. One outstanding problem is that there is a fundamental mismatch between space‐based and ionospheric estimates of the flux that is opened by each flux transfer event—in other words, their overall significance in the Dungey cycle. Spacecraft‐based estimates of the flux content of individual flux transfer events (FTEs) correspond to each event transferring flux equivalent to approximately 1% of the open flux in the magnetosphere, whereas studies based on global‐scale radar and auroral observations suggest this figure could be of the order of 10%. In the former case, flux transfer events would be a minor detail in the Dungey cycle, but in the latter they could be its main driver. We present observations of two conjunctions between flux transfer events observed by the Cluster spacecraft and pulsed ionospheric flows observed by the Super Dual Auroral Radar Network (SuperDARN) network. In both cases, a similar number of FTE signatures were observed by Cluster and one of the SuperDARN radars, but the conjunctions differ in the azimuthal separation of the spacecraft and ionospheric observations (i.e., the distance of the spacecraft from the cusp throat). We argue that the reason for the existing mismatch in flux estimates is due to implicit assumptions made about FTE structure, which tacitly ignore the majority of flux opened in mechanisms based on longer reconnection lines. If the effects of such mechanisms are considered, a much better match is found.