The semiannual oscillation in the thermosphere as a conduction mode
The semiannual oscillation in the thermosphere as a conduction mode
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DOI：
10.1029/ja087ia12p10527
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发表时间：
1982-12
影响因子：
--
通讯作者：
R. Walterscheid
中科院分区：
文献类型：
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作者：
R. Walterscheid
密度变化的半年性和相对较弱的纬向依赖性是热层密度季节变化的令人困惑的特征。这些特点是令人困惑的，因为热层加热的季节变化的年谐波是相当大的比半年，因为这两个谐波加热主要是纬度依赖。本文发展了一个热层密度半年振荡的全球一致分量模式。该分量是由热阻尼修改的振荡的传导模式。结果表明，这种振荡基本上是由焦耳加热在高纬度。模型计算的结果与观测值吻合得很好。我们认为，观测到的半年振荡的不稳定性主要是由于（1）半年传导模对全年的较强强迫和（2）成分的季节变化对纬向依赖分量的抑制。
The substantially semiannual character of the density variation and its rather weak latitudinal dependence are puzzling features of the seasonal variation of density in the thermosphere. These features are puzzling because the annual harmonic of the seasonal variation of thermospheric heating is considerably greater than the semiannual and because the heating for both harmonics is predominately latitude dependent. A model of the globally uniform component of the semiannual oscillation in thermospheric density is developed. This component is a conduction mode of oscillation modified by thermal damping. It is shown that this oscillation is essentially driven by Joule heating at high latitude. Model calculations give results which agree well with observations. It is suggested that the observed prominance of the semiannual oscillation is a consequence, primarily, of (1) the stronger forcing for the semiannual conduction mode over the annual and (2) the suppression of the latitudinally dependent components by seasonal variations in composition.