6300-Å airglow meridional intensity gradients
6300-Å airglow meridional intensity gradients
复制标题
6300-Å 气辉经向强度梯度
DOI：
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发表时间：
1980
期刊：
影响因子：
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通讯作者：
J. Meriwether
中科院分区：
文献类型：
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作者：
F. Herrero;J. Meriwether
在相当大的磁活动时期，观测到气辉纬向强度梯度（AIRGLOW）随反太阳子午线从东向西移动。梯度的大小约为0.1 R/km或更大。我们认为，这种现象的发展是由于相反的纬向中性风相遇而产生的速度梯度。北方风系统是由高纬度的极光加热产生的，它产生了穿透到夏季半球低纬度的赤道风。南风系统是由低层大气的热潮汐和白天极紫外辐射吸收的原位强迫共同形成的赤道午夜气压隆起产生的。在磁暴中，两个风系的合并产生了一个在纬度上宽达几百公里的锋面。锋面以北的电离层升高，气辉较弱。锋面以南的电离层被压低，气辉增强，表面亮度约为100 R。从这些观测中发展出来的概念模型解释了彗星的整体行为以及正常的午夜崩溃。简单计算表明，该方法不仅可以用来估计午夜气压隆起区的纬向速度梯度，而且还可以用来估计午夜气压隆起区的风速。
Airglow meridional intensity gradients (MIG) that moved from east to west with the antisolar meridian have been observed during times of considerable magnetic activity. The magnitude of the gradient is around 0.1 R/km or more. We believe the MIG phenomenon develops as a result of a velocity gradient that is produced by the meeting of opposing meridional neutral winds. The northern wind system arises from the auroral heating at high latitude that produces meridional winds penetrating to low latitudes in the summer hemisphere. The southern wind system is produced by the equatorial midnight pressure bulge that is formed by the thermal tides of the lower atmosphere combined with the in situ forcing by EUV radiation absorption in the daytime. In a magnetic storm the merging of the two wind systems produces a sharp front over a latitudinal width of several hundred kilometers. North of the front the ionosphere is elevated, and the airglow is weak. South of the front the ionosphere is depressed, and the airglow is enhanced with a surface brightness of the order of 100 R. The conceptual model that evolved from these observations accounts for the overall behavior of the MIG as well as the normal midnight collapse. A simple calculation shows that the MIG can be used to estimate the meridional velocity gradient as well as the magnitude of the winds in the midnight pressure bulge.