| dc.description.abstract | The Equatorial Ionization Anomaly (EIA) is the most pronounced low-latitude ionospheric structure, featuring two dense bands of electron density around ±15°N magnetic latitude straddling the magnetic equator. In this study, the total electron content (TEC) derived from Global Navigation Satellite System (GNSS) and Global Ionosphere Map (GIM) in 2000–2017 are utilized to examine the response of EIA crests strength, appearance time, and latitude to lunar phase, as well as lunar phase effects during the stratospheric sudden warming (SSW) and the total solar eclipse. The 18‐year statistical analysis shows that lunar phases can modulate the appearance time and latitude of the EIA crests with a 14.76-day periodicity. The EIA crests on the new moon or full moon lead those of the 18‐year average by about 20–40 minutes. By contrast, the EIA crests on the first quarter or third quarter lag those of the 18‐year average by about 20–40 minutes. Meanwhile, EIA crests move the furthest poleward and equatorward with 1° latitude 2–5 days after the new moon or full moon and the first quarter or third quarter, respectively. The maximum amplitude of 14.76-day variations in the appearance time extends to 1 hour and the latitude reaches 2°, which appears around the perihelion. By contrast, the minimum amplitude of the 14.76-day variation occurs around the aphelion. Since the appearance time of EIA crests varies with a 14.76-day period, the TEC around the new moon or full moon yields a larger value after 08:00 solar local time (SLT) but a smaller value after 14:00 SLT. On the contrary, around the first quarter or third quarter, TEC decreases after 08:00 SLT and increases after 14:00 SLT. This study further employs the GIM TEC and 12 SSW events during 2000–2013 to examine the relation between lunar phases and SSWs. The statistical analysis shows that SSWs can advance the appearance time of the EIA crests by about 0.47 hours regardless of lunar phases. However, since the modified EIA crest appearance time by the SSWs is smaller than that by the lunar phases, the TEC increases/decreases pattern is dominated by lunar phases. Thus, SSW may not result in an enhancement of TEC in the morning sector, except around the new moon or full moon days. On the other hand, the GNSS TEC is utilized to analyze the 14.76-day signatures in the solar eclipse effects of the major depression (MD), pre-ascension (PA), sunset ascension (SA), and secondary depression (SD) on 21 August 2017. The results show that due to the lunar phase effects, PAs are enhanced and suppressed before and after 14:00 SLT, respectively; SAs and SDs are suppressed and enhanced during 14:00–20:00 SLT, respectively; and MDs have been underestimated before and overestimated after 14:00 SLT. While, a reference nearby the solar eclipse day(s) can minimize the lunar phase effect but enhance solar eclipse signatures. In conclusion, lunar phases can significantly modulate the appearance time, latitude, and pattern of daily TEC of the EIA crests, which should be considered when studying an SSW or a total solar eclipse. | en_US |