Hemispheric symmetry and asymmetry of poleward moving radar auroral forms (PMRAFs) and associated polar cap patches during a geomagnetic storm
Hemispheric symmetry and asymmetry of poleward moving radar auroral forms (PMRAFs) and associated polar cap patches during a geomagnetic storm
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DOI：
10.3389/fphy.2023.1174209
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发表时间：
2023-07
影响因子：
3.1
通讯作者：
Y. Zou;Li‐Jen Chen;B. Walsh;B. Burkholder;Yuzhang Ma;W. Bristow;L. Lyons;Jiang Liu;S. Tian;S. Yadav;Antea J. Coster;K. McWilliams
中科院分区：
文献类型：
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作者：
Y. Zou;Li‐Jen Chen;B. Walsh;B. Burkholder;Yuzhang Ma;W. Bristow;L. Lyons;Jiang Liu;S. Tian;S. Yadav;Antea J. Coster;K. McWilliams
简介：磁层顶重联通过驱动快速电离层流动、极光瞬变和称为极冠斑块的高密度等离子体结构来影响昼侧电离层。然而，大多数观察到的重连的影响是有限的一个半球，并出现了一个问题，如何对称的影响之间hemispheres.Methods：我们解决这个问题，使用半球间观测极移动雷达极光的形式（PMRAFs），这是一个“化石”的签名磁层顶重连，在磁暴。我们特别感兴趣的是PMRAFs的时间重复和空间结构，这是直接影响的时间和空间变化的磁层顶重联。PMRAFs的检测和跟踪使用SuperDARN补充DMSP，Swarm，和GPS TEC measurements.Results：结果表明，PMRAFs重复发生的时间尺度约为10分钟。他们是一对一的脉冲电离层流相关，并搭配极冠补丁嵌入在电离的舌头。PMRAFs的时间重复表现出半球之间的相关性非常高，这表明PMRAFs在两个半球中以相似的速率产生，甚至是紧密同步的。然而，空间结构表现出显着的半球不对称性。在北方半球，PMRAFs/补丁有一个晨昏细长的雪茄形状，延伸>1,000 km，有时达到>2,000 km，而在南半球，PMRAFs/补丁的2-3倍short.Conclusion：有趣的对称性和不对称性的PMRAFs表明，磁层顶重联和当地电离层条件起着重要的作用，在确定PMRAFs/补丁的对称程度。
Introduction: Magnetopause reconnection is known to impact the dayside ionosphere by driving fast ionospheric flows, auroral transients, and high-density plasma structures named polar cap patches. However, most of the observed reconnection impact is limited to one hemisphere, and a question arises as to how symmetric the impact is between hemispheres.Methods: We address the question using interhemispheric observations of poleward moving radar auroral forms (PMRAFs), which are a “fossil” signature of magnetopause reconnection, during a geomagnetic storm. We are particularly interested in the temporal repetition and spatial structure of PMRAFs, which are directly affected by the temporal and spatial variation of magnetopause reconnection. PMRAFs are detected and traced using SuperDARN complemented by DMSP, Swarm, and GPS TEC measurements.Results: The results show that PMRAFs occurred repetitively on time scales of about 10 min. They were one-to-one related to pulsed ionospheric flows, and were collocated with polar cap patches embedded in a Tongue of Ionization. The temporal repetition of PMRAFs exhibited a remarkably high degree of correlation between hemispheres, indicating that PMRAFs were produced at a similar rate, or even in close synchronization, in the two hemispheres. However, the spatial structure exhibited significant hemispherical asymmetry. In the Northern Hemisphere, PMRAFs/patches had a dawn-dusk elongated cigar shape that extended >1,000 km, at times reaching >2,000 km, whereas in the Southern Hemisphere, PMRAFs/patches were 2–3 times shorter.Conclusion: The interesting symmetry and asymmetry of PMRAFs suggests that both magnetopause reconnection and local ionospheric conditions play important roles in determining the degree of symmetry of PMRAFs/patches.