Local-Time and Vertical Characteristics of Quasi-6-Day Oscillation in the Ionosphere During the 2019 Antarctic Sudden Stratospheric Warming

This study investigates new characteristics of ionospheric modulations driven by quasi-6-day wave (Q6DW) burst following a rare Antarctic sudden stratospheric warming (SSW) in September 2019. Local-time and vertical variations of the amplitude and phase of quasi-6-day oscillation (Q6DO) in the ionosphere are examined by using data assimilation analysis of electron density from three-dimensional Global Ionosphere Specification (GIS). The maximum amplitudes of Q6DO are located symmetrically ±20° off the magnetic equator at ~12 LT, with a secondary peak at 17 LT. The amplitude of Q6DO weakens at 15 LT, with a sudden phase shift, suggesting multiple dynamo processes driving the Q6DO-related ionospheric variations. The altitude-latitude structure of Q6DO shows that the ionospheric modulations extend beyond the equatorial ionization anomaly, indicating the wind dynamo source regions at higher latitudes. A likely physical mechanism is discussed based on possible interactions of Q6DW and semidiurnal migrating tides leading to the dynamo modulation and phase differences.