日环食激发大气声重力波的研究

利用1987年9月23日日环食期间在中国多个测站获得的地面微压波、无线电探空及太阳辐射资料研究了日食激发声重力波的波源机制、波谱特征、地区差异,并与同时进行的电离层探测结果进行了比较。结果表明此次日环食过程中肯定有重力波发生,其周期与太阳直接辐射起伏经历的时间有明显的一致性。不同地方的日食重力波都来自太阳直接辐射变化直接产生的强迫振荡和各地大气层内的浮力振荡。前者的波动周期较长,振幅较大,直接与日食期间太阳辐射的起伏有关;后者的波动周期较短,振幅较小,与各地日食时局地大气层内的稳定度及湿度条件有关。研究中发现由日食引起的太阳直接辐射有两种与重力波激发有关的起伏过程,一种是初亏-复圆阶段的振荡,其周期与各地日食开始时间有关;一种是复圆后的振荡,其周期与各地食分值有关。这两种起伏周期与日食参数的相关系数都在0.99以上。本文在分析日食的太阳辐射和局地大气效应的基础上,提出了相应的声重力波发生的物理机制,并讨论了日食声重力波与同时发生的电离层振荡的关系。针对70年代以来国内外一直未能解决的日食是否激发大气声重力波的问题,本文得到一个简单而重要的结论:早上发生日食的地方有长周期宽频谱的大气声重力波产生,下午发生日食的地方则没有这种波出现。

A study on atmospheric acoustic-gravity waves excited by annular solar eclipse

The mechanism of wave sources,characteristics of wave spectra and the endemic differences of gravity waves during the 23 September 1987 annular solar eclipse were investigated byusing the data of microbarometer,sounding and solar radiation.Some results were compared with the data of ionospheric disturbances observed at the same time.It was shown that gravity waves occurred really during the solar eclipse,its periods were obviously interrelated with the oscillation periods of the solar direct radiation.Gravity waves from solar eclipse originated from both coercive oscillation produced by the variations of solar direct radiation and buoyance oscillation.The former has long wave period and strong amplitude.The later is related to conditions of local stability and humidity of atmosphere,it has shorter period and weaker amplitude.It was found that there are two direct radiation oscillations which excite atmospheric gravity waves during solar eclipse.One is in the stage from first to last contact,its period is related to the local time of eclipse beginning (solar elevation).The other is after last contact,its period is related to the local magnitude of eclipse.The correlation coefficients of both the above relationships are more than 0.99
Basing on the analysis for local atmospheric effects of solar eclipse,we put forward a mechanism of occurring of gravity waves and suggest important amendments to Chimonas model.
The relations between ionospheric disturbances and gravity waves were also discussed.In connection with dispute about whether atmospheric gravity waves occur during solar eclipse,we pointed out a simple and important conclusion,that is,gravity waves possessing long period (30-150 min.) and large amplitude (10⁰-10¹ Pa) will occur where solar eclipse begins in the morning,and it would not present where eclipse occurs in the afternoon.