Climatology of polar ionospheric density profile in comparison with mid-latitude ionosphere from long-term observations of incoherent scatter radars: A review

Hemispheric Asymmetry of the Polar Ionospheric Density Investigated by ESR and JVD Radar Observations and TIEGCM Simulations for the Solar Minimum Period

“…It is clear that the model significantly overestimates (underestimates) the F-region density for the December solstice but slightly underestimates (overestimates) the density for the June solstice in the NH (SH), which results in the opposite seasonal variations to the observations. In addition, the TIEGCM reveals not only the winter anomaly in the NH but also the semiannual variation in the SH, while the observed polar ionospheric density does not exhibit any anomalous feature in the seasonal variations for low solar activity, which was also reported by our previous study (Kim et al, 2020). Qian et al (2013) reported that the observed F-region peak density (NmF2) is larger in summer than in winter during solar minimum years, but the TIEGCM exhibits higher NmF2 in winter rather than in summer at high latitudes.…”

“…The polar ionosphere is primarily governed by particle precipitations and magnetospheric electric fields in addition to solar EUV radiation, which leads to significant variations of ionospheric density with local time, season, and solar and geomagnetic activities in association with thermospheric changes in composition, winds and temperature. The climatological features of the polar ionospheric density have been presented by a number of previous studies (e.g., Cai et al., 2007; Fontaine, 2002; Kim et al., 2020; Moen et al., 2008; Xu et al., 2014). Most recently, Kim et al.…”

“…(2019) also reported the equinoctial asymmetry using GPS TEC in the southern polar region, TEC is larger in March than in September. In the northern polar region, on the other hand, the ionosphere exhibits a greater density in September than in March equinox (Kim et al., 2020). Considering these results from the previous and present studies, it can be concluded that the polar ionospheric densities seem to be greater in September (March) equinox (i.e., fall equinox) than in March (September) equinox in the NH (SH).…”

Model Simulation of SAID Intensification in the Ionosphere Under a Current Generator: The Role of Ion Pedersen Transport

“…Due to the small F‐region ion‐neutral collision frequency, the upper ionosphere is not likely to provide a major contribution to the height‐integrated Σ P . Even at night and in the absence of auroral precipitation, existing radar/rocket measurements typically reported electron densities on order of a few 10 3 cm −3 up to ∼10 4 cm −3 in the nighttime subauroral E‐region ionosphere (e.g., Chen & Harris, 1971; Kim et al., 2020; Strobel et al., 1974; Titheridge, 2000), which may still contribute to a major part of Σ P there (see Section 2.2 later for a brief discussion of the possible ionization sources there). There is so far a lack of direct observations of the electron density under intense SAID in the lower ionosphere.…”

Disappearance of the Polar Cap Ionosphere During Geomagnetic Storm on 11 May 2019

“…This range of F-region is consistent with the previous study. Kim et al (2020) statistically analyzed the electron density profiles in the polar region using long-term data observed by incoherent scatter radar. They confirmed that the altitude of F1-layer appeared around 150 km for daytime and F-region peak height varied in the range from 200 to 400 km respect to the geomagnetic conditions.…”