Local empirical model of ionospheric plasma density derived from Digisonde measurements at Irkutsk

Ionogram data from routine ionospheric observations in Irkutsk, Russia using a DPS-4 Digisonde sounder were hand-scaled for the 6-year period from December 2002 to December 2008 to derive a local empirical model of the electron density distribution in the bottomside ionosphere that provides a comprehensive description of the diurnal, seasonal, and solar activity variations of the major ionospheric characteristics. The paper describes the technique for building the local empirical model and the results of comparing its diurnal, seasonal, and solar activity specifications with the standard IRI-2007 climatological model for the same period of time, and retrospective observational data from the Millstone Hill incoherent scatter radar (1976-2002) and a collocated Digisonde (1989-1990, 1998-2004). Reasoning for the observed differences between the three datasets is then provided in terms of background physical phenomena. Primary focus of the paper is the behavior of three F(2) layer characteristics: the F(2) peak density (N(m)F(2)), the peak height (h(m)F(2)) and the bottomside thickness (B(0)).