【pdf】 LiuL.,etal.(2007),Thedependenceofplasmadensityinthetopsideionosphereonsolaractivitylevel,Ann.Geophysicae,25,1337-1343.【pdf】 LiuL.,etal.(2007),Yearlyvariationsofglobalplasmadensitiesinthetopsideionosphereatmiddleandlowlatitudes,J.Geophys.Res.,112,A07303,doi:10.1029/2007JA012283.【pdf】 LiuL...