Forcing From Lower Thermosphere and Quiet Time Scintillation Longitudinal Dependence
Forcing From Lower Thermosphere and Quiet Time Scintillation Longitudinal Dependence
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DOI：
10.1029/2020sw002610
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
E. Yizengaw;K. Groves
中科院分区：
文献类型：
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作者：
E. Yizengaw;K. Groves
几乎每天都会发生的安静时间电离层等离子体气泡成为影响通信和导航系统的射频 (RF) 信号衰减的重大威胁。我们分析了多仪器观测，以确定安静时间气泡的驱动机制，并回答长期存在的问题，即是什么控制着电离层不规则发生率的纵向和季节依赖性？虽然 VHF 闪烁和 GNSS ROTI 用于表征不规则性的发生，但 C/NOFS 上 JRO 和 IVM 的垂直漂移以及重力波 (GW) 振幅、提取的 SABRE 温度分布可用于确定产生小规模等离子体密度不规则性的潜在驱动机制。我们证明，日落后垂直漂移增强可能并不总是产生赤道等离子体气泡的必要条件。具有垂直波长（4 km < λv < 30 km）的对流层引力波也可以穿透到更高的高度，并为底侧电离层提供足够的种子并引发密度不规则性。本文通过对引力波振幅和不规则性发生分布之间的一对一比较，还证明了引力波播种在调节赤道密度不规则性的纵向依赖性方面发挥着关键作用。因此，越来越清楚的是，了解较低热层的强迫对于建模界预测电离层不规则性和闪烁的日常和纵向变化至关重要。
The quiet time ionospheric plasma bubbles that occur almost every day become a significant threat for radio frequency (RF) signal degradation that affects communication and navigation systems. We have analyzed multi‐instrument observations to determine the driving mechanism for quiet time bubbles and to answer the longstanding problem, what controls the longitudinal and seasonal dependence of ionospheric irregularity occurrence rate? While VHF scintillation and GNSS ROTI are used to characterize irregularity occurrence, the vertical drifts from JRO and IVM onboard C/NOFS, as well as gravity waves (GWs) amplitudes, extracted SABER temperature profiles, are utilized to identify the potential driving mechanism for the generation of small‐scale plasma density irregularities. We demonstrated that the postsunset vertical drift enhancement may not always be a requirement for the generation of equatorial plasma bubbles. The tropospheric GWs with a vertical wavelength (4 km < λv < 30 km) can also penetrate to higher altitudes and provide enough seeding to the bottom side ionosphere and elicit density irregularity. This paper, using a one‐to‐one comparison between GWs amplitudes and irregularity occurrence distributions, also demonstrated that the GWs seeding plays a critical role in modulating the longitudinal dependence of equatorial density irregularities. Thus, it is becoming increasingly clear that understanding the forcing from a lower thermosphere is critically essential for the modeling community to predict and forecast the day‐to‐day and longitudinal variabilities of ionospheric irregularities and scintillations.