In this paper,data of ionospheric Es-s
over Wuchang,China are analyzed and theoretical investigation are made.It shows that:(1) The occurrence of Es-s
is in proportion to a factor K=1/G(f0
(2)The occurrence of Es-s
is also clearly influenced by the power of the equipment used.(3)Es-s
seems to be a phenomenon in non-magnetically disturbed days,which is due to the fact that the observability is limited by the high fmin
in disturbed days.(4)Proper related phenomena exist both as "the prelude" and "the postlude" to the occurrence of Es-s
over Wuchang.Generally,there also exists stratification due to acoustic gravity waves.Judging from these and other ionospheric features over Wuchang,the lunar effect may serve as a common source.