There is strong correlation among the ionospheric longitudinal structures of wavenumber-3(WN3),wavenumber-4(WN4),and eastward-propagating diurnal tides with zonal wave numbers s = 2 and 3(DE2 and DE3) in the upper atmosphere.The total electron content derived from the Global Ionospheric Maps of the Jet Propulsion Laboratory is used to deduce the latitudinally total electron content(ITEC) in the low-latitude ionosphere,and TIDE/TIMED observations are employed to obtain zonal and meridian winds of the mesopause and lower thermosphere.Through Fourier transformation,various ionospheric longitudinal harmonic components and tidal patterns are derived from the ionospheric and upper-atmospheric observations,and we compare the annual/inter-annual variations in ionospheric harmonic components WN3 and WN4 with those in atmospheric tides(DE2 and DE3).It is found that the annual and inter-annual variations in WN3 and WN4 are consistent with those in DE2 and DE3 zonal wind components respectively,while they are inconsistent with those in the meridian components.We then decompose the harmonic components into "tidal patterns",finding that the "DE2" and "DE3" patterns are the main parts of WN3 and WN4 respectively.Their annual and inter-annual variations are similar to those of atmospheric tidal patterns(DE2 and DE3).Complex correlation results show that correlation between the ionospheric "DE2" in WN3 and the atmospheric tidal DE2 zonal wind component is quite strong in the Northern Hemisphere,while that between the ionospheric "DE3" in WN4 and the atmospheric tidal DE3 zonal wind component is much stronger at low latitudes.At the same time,the contribution of the meridian wind component is very weak.Above all,the atmospheric tidal DE2 and DE3 patterns are important factors of the ionospheric WN3 and WN4 structures.
电离层沿经度方向变化的3波(WN3)和4波(WN4)经度波数谱成分与高层大气中周日东向2波(DE2)和3波(DE3)潮汐模之间密切相关.利用由JPL全球电离层地图(GIM)数据计算出的总电子积分含量(TEC)的纬度积分ITEC,以及TIMED卫星搭载的TIDI仪器观测到的MLT(Mesopause and lower Thermosphere)高度上的大气水平风场,通过傅里叶变换提取出不同的电离层经度变化的波数谱成分和不同的大气潮汐模,比较了WN3和WN4等波数谱成分与DE2,DE3等潮汐模的年变化和年际变化,发现WN3,WN4的变化分别与DE2,DE3中纬向风分量的变化一致,而与其子午风分量没有明显的联系.通过进一步将电离层经度变化波数谱成分WN3和WN4分解为"潮汐模",结果显示"DE2"和"DE3"各自在WN3和WN4中起主导作用,它们的年变化和年际变化也同DE2,DE3潮汐类似.最后,复相关分析的结果表明电离层WN3中的"DE2"与大气DE2潮汐的纬向风分量在北半球有很好的相关性,电离层WN4中的"DE3"则与大气DE3潮汐的纬向风分量在整个中低纬地区相关程度很高;与此同时,子午风分量对电离层"DE2","DE3"的贡献很微弱.这些都说明大气DE2,DE3潮汐的纬向风分量是引起电离层WN3,WN4的重要因素.
