“…Since the discovery of the winter anomaly in daytime f o F 2 (the critical frequency of the F 2 layer) by Kirby et al [1934] and the semiannual effect in the F 2 region by O. Burkard in 1951, there are many studies on the ionospheric seasonal behaviors, conventionally conducted with f o F 2 or N m F 2 , and TEC [e.g., Feichter and Leitinger , 1997; Huang et al , 1989; Jakowski et al , 1981; Ma et al , 2003; Mayr and Mahajan , 1971; McNamara and Smith , 1982; Torr and Torr , 1973; Unnikrishnan et al , 2002; Yonezawa , 1971; Yu et al , 2004; Yuen and Roelofs , 1967; Zeng et al , 2008; Zou et al , 2000] as well as modelings [e.g., Millward et al , 1996; Pavlov and Pavlova , 2005; Richards , 2001].…”