The long-term trend variation of ionospheric parameter's difference at 43.8°N station of China

The difference of the month median value at two typical equilatitudinal mid-latitude stations Urumchi (43.8°N, 87.6°E) and Changchun (43.83°N, 125.2°E), China are used to study the ionpsheric long-term trend. The main results are: (1) there is no obvious long-term trend for ΔfoE. This point is different from Jarvis (2008), who use the data from the station near the boundary between the ocean and continent. (2) there are positive (increasing) trend in daytime and little negative trend in night for ΔfoF2, which is maybe related to the difference of meridional wind. There are notable seasonal variations: the negative trend with minimum in summer, positive trend with maximum in equinox. (3) The ΔhmF2 show negative trend in all month and local time. There is a minimum at noon in June and larger value in other seasons. The trend of ΔhmF2 is maybe related to the spatial variability in the trend of thermosphere.