Comment on “The winter anomaly in the middle‐latitude F region during the solar minimum period observed by the Constellation Observing System for Meteorology, Ionosphere, and Climate” by W. K. Lee, H. Kil, Y.‐S. Kwak, Q. Wu, S. Cho, and J. U. Park

Winter anomaly in NmF2 and TEC: when and where it can occur

“…This fact is elucidated by the essential difference between the halfthicknesses of the electron density winter and summer profiles. According to (Mikhailov & Perrone, 2014), the small half-thickness of the electron density winter profile, N e (h), as compared with that of the summer one, is the reason for the winter/summer ratio decrease at the heights different from the maximal ones.…”

“…The definition of the winter anomaly given initially for N m F 2 (or f o F 2 ) may be applied for other ionospheric parameters. Considering the winter anomaly in the electron density at a given height N e (h), it was found that the winter anomaly exists only over a limited height range (from~180 km up to 400-500 km) around the peak height (King et al, 1968;Fatkullin, 1970;Boenkova & Mednikova, 1972;Lee et al, 2011;Mikhailov & Perrone, 2014). The detailed explanation of this feature was given by Mikhailov & Perrone (2014).…”

“…Recent papers that focused on the winter anomaly study (Lee et al, 2011;Pavlov & Pavlova, 2012;Burns et al, 2014;Mikhailov & Perrone, 2014;Lee et al, 2014) demonstrated the importance of this topic in the ionospheric community and some uncertainties that should be resolved. Historically, the winter anomaly was found and studied using N m F 2 (or f o F 2 ) from ionosonde observations, but the global ionosonde distribution is not uniform and does not cover all world regions.…”

Solar Hysteresis Pattern and Spectral Components in TEC Time Series (GPS and TIE‐GCM) of the Quadrilaterally Coupled Geomagnetic Conjugate Low‐Latitude Stations

“…Even though the model includes the seasonally varying eddy diffusion, TIE‐GCM version 2.0 still dissimulates a seasonal component (∼280‐day), which is not compatible with the observations from southern low‐latitudes. It is because seasonal variation (changes in electron density from summer to winter) is complicated owing to solar flux (Mikhailov & Perrone, 2014; Rao, Chakraborty, et al., 2019), regional (Huo et al., 2009; Yasyukevich et al., 2018; Zhao et al., 2007), and altitude dependency (Liu et al., 2007; Mikhailov & Perrone 2014; Su et al., 1998; Torr & Torr, 1973; Zhao et al., 2005). These factors were not taken care of in TIE‐GCM version 2.0.…”

“…In light of above, it may be said that the TIE‐GCM assumes the seasonal component as a result of the application of seasonally varying eddy diffusion in TIE‐GCM version 2.0 to account for seasonal fluctuation of O/N2. It is because the Rishbeth theory (Rishbeth et al., 1978) could not be fully applied to explain the latest results of the TEC winter anomaly (Mikhailov & Perrone, 2014; Rao, Chakraborty, et al., 2019; Yasyukevich et al., 2018).…”