The collapse of the midnight ionosphere and behavior of meridional neutral winds at Townsville over a full solar cycle
The collapse of the midnight ionosphere and behavior of meridional neutral winds at Townsville over a full solar cycle
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DOI：
10.1002/2015ja021842
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发表时间：
2015-11
期刊：
影响因子：
--
通讯作者：
P. Dandenault;P. Richards
中科院分区：
文献类型：
--
作者：
P. Dandenault;P. Richards
本文研究了 1970 年至 1980 年春分期间澳大利亚汤斯维尔电离层突然下降（午夜塌陷）的原因。在所调查的 330 个春分之夜中，89% 的 hmF2 午夜塌陷发生在午夜，三月春分期间午夜塌陷的平均震级为 84 公里，九月春分期间午夜崩溃的平均震级为 99 公里。 hmF2 的观测用于使用第一原理物理模型确定等效的经向中性风。对这些派生风的谐波分析表明存在显着的昼间（24 小时）、半日（12 小时）和昼间（8 小时）潮汐分量。风谐波对午夜崩溃的贡献是通过对风进行带通滤波以仅允许某些潮汐，然后对其在午夜附近对 hmF2 的影响进行建模来确定的。结果表明，经向中性风的日间、半日间和昼间分量在各个时刻都发挥了显着的作用，但6 h风分量的影响很小。光谱分析还表明，日间风分量在太阳活动极大期期间占主导地位。电场似乎并不是造成午夜 hmF2 塌陷的原因，因为在日本秋田的近共轭台站很少看到这种情况。
This paper investigates the causes of the sudden descent (midnight collapse) of the ionosphere at Townsville, Australia, during the equinox periods of years between 1970 and 1980. The collapse of hmF2 at midnight is found to occur on 89% of the 330 equinox nights that are investigated, and the mean magnitude of the midnight collapse is 84 km in the March equinox periods and 99 km in the September equinox periods. Observations of hmF2 are used to determine equivalent meridional neutral winds using a first principles physics model. Harmonic analysis of these derived winds reveals the existence of significant diurnal (24 h), semidiurnal (12 h), and terdiurnal (8 h) tidal components. The contribution of wind harmonics to the midnight collapse is determined by band‐pass filtering the winds to only allow certain tides and then modeling their effect on hmF2 near midnight. The results indicate that the diurnal, semidiurnal, and terdiurnal components of the meridional neutral wind all play a significant role at various times, but the effect of the 6 h wind component is minimal. The spectral analysis also reveals that the terdiurnal wind component becomes dominant during solar maximum. Electric fields do not appear to be responsible for the midnight hmF2 collapse because it is seldom seen at the near‐conjugate station of Akita, Japan.