低纬(海南)地区电离层偶发E层的潮汐类周期研究

基于低纬(海南)台站(19.5°N,109.1°E)电离层测高仪在2004年观测到的偶发E层(Es)临界频率(f₀E_s)和虚高(h'E_s)数据,利用谱分析方法,给出了中国低纬地区Es层在全年和不同季节内的短周期变化特性.对全年数据谱分析表明,Es层除具有非常强的24h周期外,还具有显著的12h和8h周期.对不同季节内两个参数的谱分析进一步表明,8h周期主要出现在f₀E_s参数的春秋分季和夏末及在h'E_s参数的几乎所有季节;6h周期主要出现在f₀E_s参数的11-12月.海南低纬Es层中具有显著的6h和8h周期特性,特别是这两个周期还能同时出现在冬季,这是以往研究中不曾发现的新结果.初步分析认为,Es层的6h和8h周期极可能是分别由1/4日和1/3日潮汐所造成的. 

Tidelike Periodicities of Ionospheric Sporadic E Observed at Low Latitude Hainan Station

The time series of the ionospheric Sporadic E (Es) critical frequency (f₀E_s) and its virtual height (h'E_s) were performed on a large database of DPS-4 ionograms recorded at Hainan station (19.5°N, 109.1°E) in 2004 to investigate the features of tidelike periodicity variations in low latitude. On yearly spectra, there was pronounced 8-hour periodicity in low latitude Es in addition to the well known 24-and 12-hour tidal variations. The yearly average phases of 24-, 12-, and 8-hour periodicities for f₀E_s (h'E_s) were at 13:00LT (13:00LT), 11:00LT (09:00LT), and 09:30LT (09:30LT). On every two-month spectra, the results showed that (1) the 24-hour periodicity in Es was the most pronounced in each season; (2) The 12-hour periodicity in Es was outstanding in each season except in January-February months; (3) The 8-hour periodicity was remarkable in equinoxes and July-August months for f₀E_s, and it was notable in almost each season for h'E_s; (4) The 6-hour periodicity mainly occurred in November and December for f₀E_s, whereas for h'E_s it appeared more in summer and winter, and weakly in equinox months. It is clearly distinct from previous results by the fact that the 6-and 8-hour periodicities in Es layer at Hainan station can occur in winter or other seasons. The 6-and 8-hour periodicities in Es layer most probably are caused by the quarter-diurnal and terdiurnal tide components, which needs to be investigated further by combining the observations and modeling of local tide.