Quiet-time seasonal behaviour of the ionosphere measured by the Ionosphere PhotoMeter (IPM) on the Chinese meteorological satellite FY-3D compared with the IRI2016 model predictions.

In this paper, we examine the climatology structure of the mid-night ionosphere at approximately two o'clock local time of a low-solar-activity year and discrepancies between Ionosphere PhotoMeter (IPM) observations and IRI (International Reference Ionosphere) model-2016 predictions using (1) a global structure for the F 2 layer peak electron density (N m F 2) for four seasons, (2) the mean N m F 2 values at different latitudes by month, and (3) the monthly distribution of the global average of N m F 2. The data is collected by the IPM, a far-ultraviolet nadir- viewing photometer that has been aboard the second-generation, polar-orbiting Chinese meteorological satellite Feng-Yun 3D (FY-3D) since its launch on November 25th, 2017 and has provided excellent opportunities for many scientific investigations of the ionosphere. We collected night glow data under low geomagnetic activity (KP ≤ 4) during 2018, and the data obtained five days before and after a full-moon night were removed to prevent the influence of stray light. Before analysing the climatology of the ionosphere and comparing the results with those obtained from IRI2016, the accuracy of N m F 2 measured by IPM was evaluated by comparison with data from ground-based ionosondes. A statistical comparative analysis of N m F 2 measured by IPM and ionosonde indicated a difference of 20% at middle latitudes and 28% at low latitudes. The global behaviour of N m F 2 measured by IPM and IRI for four seasons shows that the IRI model generally captures the morphology of the latitudinal structure and hemispheric asymmetry in N m F 2 observed by IPM. A comparison between IPM-measured N m F 2 and IRI-predicted N m F 2 indicates that the former is systematically lower than the latter. The difference in the measurements and predictions can be as large as 300%. [ABSTRACT FROM AUTHOR]