Temporal and spatial aspects of the cusp inferred from local and global ground- and space-based observations in a case study
Temporal and spatial aspects of the cusp inferred from local and global ground- and space-based observations in a case study
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DOI：
10.1029/2003ja010121
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发表时间：
2004-04
影响因子：
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通讯作者：
C. Farrugia;P. Sandholt;R. Torbert;N. Østgaard
中科院分区：
文献类型：
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作者：
C. Farrugia;P. Sandholt;R. Torbert;N. Østgaard
[1]全球和当地的观测，从地面和空间设施，承担了解的起源，观察到3小时前的行星际磁场的特点是强烈的积极的，条件下，尖点被认为是转移午后的一个阶梯状的尖点离子分散。我们的主要目的是区分时间和空间的尖点特征。斯瓦尔巴群岛的当地观测是从大约0900 - 1200 MLT扇区，而原位观测是从极地0900 MLT。全球极光观测是由Polar上的地球相机获得的。从地面的角度来看，极光似乎是一个周期性的增亮事件序列，位于大约1030 MLT中心的“正午间隙极光”的两侧。正午时分，极光以半周期性的一系列增亮现象出现。这些都是同时与高架电离层霍尔电流的增强。Polar观测到两个阶梯式离子能量-纬度色散。这两个步骤反过来又与两个连续的极光增亮事件同时发生。我们认为，从这个补充的意见，阶梯尖是时间的性质，并导致随时间变化的重联过程。全球紫外线图像被用来补充地面观测，以便将时间和空间方面分开。成像仪捕捉到，即，在中午前和中午后的扇区，两个波段的强紫外线辐射，在这两个波段之间出现了持续的弱紫外线极光。我们认为这是一个潜在的空间底层。斑片状和突发性的紫外增强与当地地面和空间测量中看到的瞬变相吻合，进一步证实了我们在尖点的空间和时间之间的区别。比较这些推论与最近的工作，在磁层顶的昼侧极光重联的反应，我们发现一个密切的对应关系。此外，我们的文件与阶梯尖，这反过来，与最近的理论思想相比，有利的场向电流。这项工作是一个贡献，目前的辩论的性质阶梯尖，并建议，多个数据集是必不可少的研究这个问题。
[1] Global and local observations, from both ground and space facilities, are brought to bear to understand the origin of a stepped cusp ion dispersion observed 3 hours prenoon under an interplanetary magnetic field characterized by strongly positive By, conditions under which the cusp is believed to be shifted postnoon. Our main aim is to distinguish the temporal from the spatial cusp features. The local observations from Svalbard are from approximately the 0900–1200 MLT sector, while the in situ observations are from Polar at 0900 MLT. The global auroral observations were acquired by the Earth camera on Polar. The aurora from the ground perspective appeared as a periodic sequence of brightening events located on either side of a “midday gap aurora” centered at about 1030 MLT. At noon the aurora appeared as a semiperiodic sequence of brightening events. These were concurrent with enhancements of the overhead ionospheric Hall current. Polar observed two steps of a staircase ion energy-latitude dispersion. These two steps were, in turn, concurrent with two consecutive auroral brightening events. We argue from this complement of observations that the stepped cusp was temporal in nature and resulted from a time-varying reconnection process. Global UV imagery was employed to complement the ground observations for the purpose of separating the temporal from the spatial aspects. The imager captured, namely, two bands of strong UV emission in the prenoon and postnoon sectors, between which there appeared a persistent, weak UV aurora. We interpret this to be an underlying spatial substratum. Patchy and bursty UV enhancements coincided with the transients seen in the local ground and space measurements, corroborating further our distinction between space and time in the cusp. Comparing these inferences with recent work on the response of the dayside aurora to reconnection at the magnetopause, we find a close correspondence. In addition, we document the field-aligned currents associated with the stepped cusp, which, in turn, compare favorably with recent theoretical ideas. This work is a contribution to the current debate on the nature of the stepped cusp and suggests that multiple data sets are essential to study this problem.