早在1970年代，科学家就预测，当日食月影在大气中以超音速移动，激发低层大气的重力波，能产生艏波。2009年7月22日全日食期间，广布东亚密集的地面全球导航卫星系统记录的电离层全电子含量，不仅完整观测了日食艏波(bow wave)，还发现了艉波(stern wave)。然而，2017年8月21日全日食的艏波则类似于冲击波，无完整明显的艉波被发现。同样是月影由西向东划过地球大气，为何这两个日食产生了不同的艏艉波？为了回答这个问题，首先，本项目将使用非线性方法完整分析日食期间不同尺度的波动，分析数据为全电子含量，掩星卫星的电离层电子浓度，电离层测高仪参数，卫星大气温度等。接着，使用地基和天基电子浓度数据，建立和研究日食期间电离层三维电子浓度结构。最后，使用电离层理论模式重制日食期间电离层结构和动力的改变。研究全日食艏艉波形成的物理机制。

Since 1970, scientists have speculated that a “bow wave” appears around the moon shadow of total solar eclipse if the source velocity exceeds the propagation speed of atmospheric gravity waves. The ground-based GNSS (Global Navigation Satellite System) TEC (total electron content) observations show the bow and stern waves in the eastern Asia longitudinal during the total solar eclipse on 22 July 2009. However, the massive TEC observation shows that the bow wave is induced by the acoustic gravity wave at the ionospheric altitude over the continent of United States during the 23 August 2017 total solar eclipse. No obvious stern wave appears during the 2017 eclipse. To answer the question of why the bow and stern waves of the two eclipses are different. In this proposal, we first apply the nonlinear time-frequency analysis method to examine the wavy structures of the electron density from GNSS, radio occultation, and ionosonde. The temperature profiles from TIMED/SABER (Thermosphere Ionosphere Mesosphere Energetics Dynamics / Sounding of the Atmosphere using Broadband Emission Radiometry) will also be examined. Moreover, we will construct the three-dimensional electron density structure using GNSS TEC and radio occultation electron density profiles during the eclipses. Eclipse effects on ionospheric electron density structure and dynamics will be simulated using TIE-GCM (National Center for Atmospheric Research, Thermosphere-Ionosphere- Electrodynamics General Circulation Model). It can be expected that the ionospheric electron density gradients and change of background structure/dynamics benefit the occurrence of plasma instabilities during the eclipse that could attribute to the formation of the bow and stern waves.