Abstract: 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.