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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Dayside magnetosphere-ionosphere coupling during IMF clock angle ～90°: Longitudinal cusp bifurcation, quasi-periodic cusp-like auroras, and traveling convection vortices
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Dayside magnetosphere-ionosphere coupling during IMF clock angle ～90°: Longitudinal cusp bifurcation, quasi-periodic cusp-like auroras, and traveling convection vortices

机译：IMF时钟角度〜90°期间的日磁层-电离层耦合：纵向尖瓣分叉，准周期尖瓣样极光和行进对流涡旋

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摘要

In spite of the great progress achieved in the understanding the Earth's magnetosphere-ionosphere system, its configuration and dynamics during periods with large horizontal interplanetary magnetic field (IMF ∣B y ∣ 0) is still poorly investigated. In such time intervals, the cusp/low-latitude boundary layer (LLBL) entry regions are characterized by a more complex magnetic reconnection topology, than during IMF B z -dominated periods, which in turn leads to peculiar magnetosheath plasma injections into the magnetosphere and associated ionospheric signatures. In this context, we discuss the 19 December 2002 dayside aurora activity, observed by the ITACA2 twin all-sky camera system, along the Greenland-Svalbard sector, during a nearly horizontal IMF (B y ～ 15 nT and B z ～ 0). The event originates from a longitudinally bifurcated cusp configuration and then develops into quasi-periodic red aurora activations, between about 1000 and 1140 UT. By analyzing the Greenlandic magnetometer data, we identify a series of westward traveling convection vortices (TCVs), moving away from magnetic noon at 2–3 km/s and synchronized with the transit of red-dominated auroral forms. We find that the auroral emission takes place in coincidence with the ionospheric footprint of the downward field-aligned currents (counterclockwise TCVs), instead of the upward ones (clockwise TCVs), as it would be expected for precipitating electrons. This fact and several analogies with previously reported quasi-periodic TCV activity, observed during IMF B y -dominated periods, suggest that the geomagnetic activity could be associated with FACs that are triggered by the magnetic merging on the dayside, either by inducing azimuthal pressure gradients at the magnetopause or by driving magnetopause/LLBL wave activity.
机译：尽管在了解地球磁层-电离层系统方面取得了巨大进展，但在水平行星际磁场大（IMF ∣B y ∣ 0）期间，其结构和动力学仍然缺乏研究。在这样的时间间隔中，尖峰/低纬度边界层（LLBL）进入区域的特征在于，与在IMF B z主导的时期相比，磁重连接拓扑更为复杂，这反过来又导致向磁层和磁层注入特殊的磁荒等离子。相关的电离层签名。在这种情况下，我们讨论了由ITACA2双全天相机系统在格陵兰-斯瓦尔巴特群岛沿近水平IMF期间（B y〜15 nT和B z〜0）观察到的2002年12月19日的日间极光活动。该事件起源于纵向分叉的尖瓣构型，然后发展为准周期的红色极光激活，大约在1000和1140 UT之间。通过分析格陵兰磁强计数据，我们确定了一系列向西移动的对流涡流（TCV），它们以2-3 km / s的速度远离磁正午运动，并且与以红色为主的极光形式的传播同步。我们发现，极光发射与向下的场对准电流（逆时针TCVs）而不是向上的电场（顺时针TCVs）的电离层足迹一致，因为这可能会沉淀电子。这个事实以及在IMF B y主导时期观察到的与以前报道的准周期TCV活动的一些类比表明，地磁活动可能与日间磁合并触发的FAC有关，或者是通过诱发方位角压力梯度磁致停滞或通过驱动磁致停滞/ LLBL波活动。

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