由于IMF $\mathit{B}_{x}$引起的极向极光卵黄昏区的强度不对称
Intensity asymmetries in the dusk sector of the poleward auroral oval due to IMF $\mathit{B}_{x}$
摘要：
在地球极光全球尺度特征的研究中，行星际磁场（IMF）的径向分量很少受到关注。本文研究了当IMF位于$\textit{xz}$平面上时，两半球的全球极光响应。我们提出了一个统计研究的平均极光响应在12-24磁当地时间（MLT）部门的一个$\textit{x}$组件在IMF。两个IMF $\mathit{B}_{x}$主导的条件下（$ \pm $ IMF $\mathit{B}_{x}$）的极光强度在两个半球的地图显示期间的负IMF $\mathit{B}_{z}$，小IMF $\mathit{B}_{y}$，和当地的冬天。这是利用IMAGE卫星上的宽带成像照相机的全球成像获得的。分析表明，在两个半球的两个IMF $\mathit{B}_{x}$占主导地位的条件之间的显着不对称。在北半球，在负IMF $\mathit{B}_{x}$期间，极光在15-19 MLT区域更亮。在南半球，当IMF $\mathit{B}_{x}$为正值时，极光在16-20 MLT扇区中更亮。我们解释的背景下，一个更有效的太阳风发电机在一个半球的结果。强度不对称性和它的位置都与这一思想相一致。这一点在早些时候已经从两个半球同时观测极光的案例研究中提出，但迄今为止从未从统计研究中观察到对两个半球的全球极光亮度产生普遍影响。两个IMF $\mathit{B}_{x}$病例之间观察到的不对称性并不大;但是，在95%置信水平下差异显著。由于研究中检查的太阳风条件相当普遍（37%的时间），这种小影响的累积效应可能对总能量预算很重要。
英文摘要：
In the exploration of global-scale features of the Earth's aurora, little attention has been given to the radial component of the Interplanetary Magnetic Field (IMF). This study investigates the global auroral response in both hemispheres when the IMF is southward and lies in the $\textit{xz}$ plane. We present a statistical study of the average auroral response in the 12-24 magnetic local time (MLT) sector to an $\textit{x}$ component in the IMF. Maps of auroral intensity in both hemispheres for two IMF $\mathit{B}_{x}$ dominated conditions($ \pm $ IMF $\mathit{B}_{x}$) are shown during periods of negative IMF $\mathit{B}_{z}$, small IMF $\mathit{B}_{y}$, and local winter. This is obtained by using global imaging from the Wideband Imaging Camera on the IMAGE satellite. The analysis indicates a significant asymmetry between the two IMF $\mathit{B}_{x}$ dominated conditions in both hemispheres. In the Northern Hemisphere the aurora is brighter in the 15-19 MLT region during negative IMF $\mathit{B}_{x}$. In the Southern Hemisphere the aurora is brighter in the 16-20 MLT sector during positive IMF $\mathit{B}_{x}$. We interpret the results in the context of a more efficient solar wind dynamo in one hemisphere. Both the intensity asymmetry and its location are consistent with this idea. This has earlier been suggested from case studies of simultaneous observations of the aurora in both hemispheres, but hitherto never been observed to have a general impact on global auroral brightness in both hemispheres from a statistical study. The observed asymmetries between the two IMF $\mathit{B}_{x}$ cases are not large; however, the difference is significant with a 95% confidence level. As the solar wind conditions examined in the study are rather common (37% of the time) the accumulative effect of this small influence may be important for the total energy budget.
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