Association of Pi2 pulsations and pulsed reconnection: ground and Cluster observations in the tail lobe at 16 R E
Association of Pi2 pulsations and pulsed reconnection: ground and Cluster observations in the tail lobe at 16 R E
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DOI：
10.5194/angeo-24-3433-2006
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发表时间：
2006-12
影响因子：
1.9
通讯作者：
A. Keiling;M. Fujimoto;H. Hasegawa;F. Honary;V. Sergeev;V. Semenov;H. Frey;O. Amm;H. Rème;I. Dandouras;E. Lucek
中科院分区：
文献类型：
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作者：
A. Keiling;M. Fujimoto;H. Hasegawa;F. Honary;V. Sergeev;V. Semenov;H. Frey;O. Amm;H. Rème;I. Dandouras;E. Lucek
Cluster 航天器和几个地面站（SAMNET、IMAGE、Kakioka、Hermanus）的同步测量为 Pi2 脉动和磁尾中脉冲重联的关联提供了证据。 2002 年 9 月 8 日，在 16 R E 尾部记录到与亚暴相关的 Pi2 脉动具有相同的波形（相同的频率），并在地面（夜间和白天）上延迟，跨越 L 值从 1.23 到 6.11。尾瓣 Pi2 脉动是一系列以 600-800 km/s 的速度向地球传播的夜侧通量传输事件 (NFTE) 脉冲，首次将这两种磁层现象联系起来。 NFTE 之前被认为是尾部重连的远程签名。 Pi2 脉动的第一次地面爆发发生在高纬度和中纬度地面站，相对于尾瓣 Pi2 有约 30 秒的时间延迟，其次是低纬度地面站。最大的脉动出现在靠近极冠边界的高纬度地区（比低纬度地区大十倍）。 H-D 平面中接地 Pi2 的极化图案与周期性驱动的场对准电流 (FAC) 系统一致。此外，由于地面站之间的传播效应以及白天低纬度Pi2的同时出现，快模波也一定在内磁层中发挥了作用。极光增亮发生在上流的FAC区域，极光电喷流与极光隆起一起向极地扩展，都是典型的亚暴特征。因此，我们得出结论，16 RE 和地面上与亚暴相关的 Pi2 脉动是由磁尾中的脉冲重联远程驱动的，也就是说，重联不仅提供了能量，而且其时间变化也决定了 Pi2 的特征频率。讨论了解决电离层中脉冲重联和驱动电流系统的连接的方案。这些结果表明，重新连接可以通过现象学上称为 Pi2 脉动的方式与电离层耦合。作为推论，结果表明事件的时间历史符合修正的 NENL 亚暴模型。
Simultaneous measurements from the Cluster spacecraft and several ground stations (SAMNET, IMAGE, Kakioka, Hermanus) provide evidence for an association of Pi2 pulsations and pulsed reconnection in the magnetotail. On 8 September 2002, substorm-related Pi2 pulsations were recorded with the same waveform (same frequency) in the tail lobe at 16 R E and time-delayed on the ground (both nightside and dayside) spanning L values from 1.23 to 6.11. The tail lobe Pi2 pulsations were a series of nightside flux transfer event (NFTE) pulses propagating at a speed of 600–800 km/s towards Earth, which for the first time relates these two magnetospheric phenomena. NFTEs have previously been considered as the remote signature of tail reconnection. The first ground onset of the Pi2 pulsations occurred at high- and midlatitude ground stations with a time delay of ~30 s with respect to the tail lobe Pi2, followed by lower latitude ground stations. The largest pulsations were observed at high latitude (ten times larger than at low latitude) near the polar cap boundary. The polarization pattern of the ground Pi2s in the H-D plane was consistent with a periodically driven field-aligned current (FAC) system. In addition, fast mode waves must have also played a role in the inner magnetosphere because of propagation effects among ground stations and because of the simultaneous occurrence of dayside low-latitude Pi2. Auroral brightening occurred in the region of upflowing FAC, and the auroral electrojet expanded poleward together with the auroral bulge both of which are typical substorm signatures. Hence, we conclude that the substorm-related Pi2 pulsations in space at 16 R E and on the ground were remotely driven by pulsed reconnection in the magnetotail, that is, reconnection not only provided the energy but its temporal variations also determined the characteristic Pi2 frequency. Scenarios are discussed that address the connection of pulsed reconnection and the driven current system in the ionosphere. These results show that reconnection can be coupled to the ionosphere through what is phenomenologically known as Pi2 pulsations. As a corollary, it is shown that the time history of events fits within the modified NENL model of substorms.