声重波激发的赤道 Spread—F 不稳定性

本文导出了声重波扰动与赤道电离层扩展F层相互作用的基本方程,并对数值模拟结果进行了讨论。结果表明当声重波扰动与Kavleigh-Taylor不稳定性共同作用于赤道F层时,将导致大尺度波状结构的Spread-F.其特征为以一定速度漂移的准周期不规则性,发展到后期伴有羽柱形状的bubble(电子密度低区)产生。这种现状的bubble可上升至F层顶部并发生倾斜。声重波波矢量的方向决定着羽柱的倾斜方向。这些结果与实验观测特征相符,说明声重波扰动不仅是大尺度Saread-F的触发源,而且对其整个形态发展过程起着重要的作用。 

EQUATORIAL SPREAD-F INITIATED BY ACOUSTIC-GRAVITY WAVES

The basic equation discribing Spread--F instability with the existance of acousticgravity waves in the ionospheric F region are derived and the numerical simulationsfor certain cases are conducted. The results show that the Spread-F will occur inlarge-scale wavelike structures under the conbined action of acoustic-gravity wavesand the Rayleigh Taylor instability in the equatorial F region. This Spread-F is aquasi-periodic instability moving at certain velocity and at late;developing stage itwill form plumelike plasma density depletions (bubbles) which can rise well abovethe F peak and become tilt. The acoustic-gravity wave vector determines the tiltdirection of bubbles. All these results are in agreement with the main observationalcharacteristics. It is thought then that acoustic-gravity waves are not only one ofthe initial sources of large-scale Spread-F, but also play an important role on itswhole evolutions.