A dawn–dusk asymmetry in many high-latitude ionospheric and magnetospheric phenomena, including the aurora, can be linked to the east–west (y) component of the interplanetary magnetic field (IMF). Owing to the scarcity of observations in the Southern Hemisphere, most of the previous findings are associated with the Northern Hemisphere. It has long been suspected that if the IMF By component also produces a dawn–dusk asymmetry and/or a mirror image in the Southern Hemisphere as predicted by some theories. The present study explores the effect of the IMF By component on the dayside aurora from both hemispheres by analyzing the auroral emission data from the Global UltraViolet scanning spectrograph Imager on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics mission spacecraft from 2002 to 2007. The data set comprises 28,774 partial images of the northern hemispheric oval and 29,742 partial images of the southern hemispheric oval, allowing for a statistical analysis. It is found that even though auroras in different regions of the dayside oval respond differently to the orientation of the IMF By component, their responses are opposite between the two hemispheres. For example, at ~ 1400–1600 MLT in the Northern Hemisphere, where the so-called 1500 MLT auroral hot spots occur, peak auroral energy flux is larger for negative IMF By comparing to positive IMF By. The response is reversed in the Southern Hemisphere. The present study also suggests that the total energy flux does not change with the IMF By orientation change. This result is consistent with a larger (smaller) convection vortex in the postnoon sector for IMF By < 0 (By > 0) resulting from anti-parallel merging.

中文翻译：

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行星际磁场y分量对白天极光的影响

在许多高纬度电离层和磁层现象中，包括极光，其黎明至黄昏的不对称性可能与行星际磁场（IMF）的东西方向（y）有关。由于南半球缺乏观测资料，以前的大部分发现都与北半球有关。长期以来人们一直怀疑，IMF By分量是否还会像某些理论所预测的那样在南半球产生黎明-黄昏不对称和/或镜像。本研究通过分析2002年至2007年热球电离层中层能动学和动力学任务航天器上的全球紫外扫描光谱仪成像仪的极光发射数据，探索了IMF组分对两个半球日间极光的影响。数据集包括28个 北半球椭圆形的774个局部图像和南半球椭圆形的29,742个局部图像，可以进行统计分析。已经发现，即使在日间椭圆形的不同区域中的极光对IMF By分量的方向做出不同的响应，但它们在两个半球之间的响应却是相反的。例如，在北半球约1400-1600 MLT处，发生所谓的1500 MLT极光热点，与正IMF By相比，负IMF的峰值极光能量通量更大。在南半球的反应是相反的。本研究还表明，总能量通量不会随着IMF方向变化而变化。此结果与IMF在午后扇区中较大（较小）的对流涡旋相符。<0（按>