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

Abstract

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.,

Validation of Ionospheric Specifications During Geomagnetic Storms: TEC and foF2 During the 2013 March Storm Event‐II

“…Most simulations appear to predict foF2 and/or TEC better in NA and worse in SH (except for 12_TIE-GCM for foF2 and 12_CTIPE for TEC). This hemispheric asymmetry in the performance of the models may readily be expected from the fact that the ionospheric density structures in SH are typically more complex and therefore relatively less understood compared with the density structures in NH, mainly due to more complex structure of the geomagnetic field, for example, larger declination and larger offset between geographic and magnetic poles in SH (e.g., Jee et al, 2009;Laundal et al, 2017;Kim et al, 2023) and resulting hemispheric asymmetry in thermospheric O/N 2 ratio (Qian et al, 2022). Shim et al (2018) also suggested that this hemispheric asymmetry is possibly partly attributed to the fact that the models do not include the energy input from the inner magnetosphere that affects the ionosphere (e.g., foF2 and TEC enhancements) in the South Atlantic Anomaly (SAA) region (Dmitriev et al, 2017;Zhao et al, 2016) where the 4 stations in SH are situated nearby.…”

“…Most simulations appear to predict foF2 and/or TEC better in NA and worse in SH (except for 12_TIE‐GCM for foF2 and 12_CTIPE for TEC). This hemispheric asymmetry in the performance of the models may readily be expected from the fact that the ionospheric density structures in SH are typically more complex and therefore relatively less understood compared with the density structures in NH, mainly due to more complex structure of the geomagnetic field, for example, larger declination and larger offset between geographic and magnetic poles in SH (e.g., Jee et al., 2009; Laundal et al., 2017; Kim et al., 2023) and resulting hemispheric asymmetry in thermospheric O/N 2 ratio (Qian et al., 2022). Shim et al.…”