Dawn‐Dusk Confinement of Magnetic Reconnection Site in the Near‐Earth Magnetotail and Its Implication for Dipolarization and Substorm Current System
Dawn‐Dusk Confinement of Magnetic Reconnection Site in the Near‐Earth Magnetotail and Its Implication for Dipolarization and Substorm Current System
复制标题
近地磁尾磁重联位点的黎明-黄昏约束及其对偶极和亚暴流系统的意义
DOI：
10.1029/2021ja029691
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Shinohara Iku
中科院分区：
文献类型：
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作者：
Nagai Tsugunobu;Shinohara Iku
在地磁尾观测的基础上，建立了近地磁尾磁重联场的晨昏约束。在1994年至2019年期间，Geotail已经与近地球磁尾中径向距离为20-30 RE的亚暴发生关联的磁重联进行了50多次遭遇。对这些事件的地面磁场观测进行了检查，对有限数量的情况对地球同步航天器观测进行了调查。磁场重联点位于由中纬度地磁场变化产生的大尺度亚暴电流系统的向上（从电离层到尾）场向电流部分。该地点仅限于当地时间1小时的局部黎明-黄昏范围，就在大规模亚暴电流系统中心的以西。X线的黎明-黄昏长度很短，这意味着磁重联本质上是磁尾纬向平面中的二维动力学。在地球同步轨道上，磁场重联点的子午线附近会出现快速偶极和向上的场向电流。这项研究表明，磁层内部的快速偶极化是由磁重联产生的向地外流产生的，强烈的向上场向电流是磁重联的直接后果。
The dawn‐dusk confinement of magnetic reconnection site in the near‐Earth magnetotail is established on the basis of Geotail observations. Geotail has made more than 50 encounters with magnetic reconnection in association with the onset of substorms in the near‐Earth magnetotail at radial distances of 20–30 REin the period of 1994–2019. Ground magnetic field observations are examined for these events, and geosynchronous spacecraft observations are investigated for a limited number of cases. The magnetic reconnection site is located in the upward (from the ionosphere to the tail) field‐aligned current part of large‐scale substorm current system derived from ground midlatitude magnetic variations. The site is confined to the localized dawn‐dusk extent of the 1‐hr local time, just west of the center of the large‐scale substorm current system. The short dawn‐dusk length of the X‐line implies that magnetic reconnection inherently proceeds as the two‐dimensional dynamics in the magnetotail meridional plane. Rapid dipolarization with upward field‐aligned currents occurs at geosynchronous altitude near the meridian of the magnetic reconnection site. This study demonstrates that rapid dipolarization in the inner magnetosphere is produced with earthward outflows from magnetic reconnection and that intense upward field‐aligned currents are a direct consequence of magnetic reconnection.