Day-to-day variability of the equatorial ionosphere in Asian sector during August–October 2019

• Published in: Frontiers in Astronomy and Space Sciences
• Main Authors: Liu, Huixin, Otsuka, Yuichi, Hozumi, Kornyanat, Yu, Tao
• Other Authors: Japan Society for the Promotion of Science
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2023
• Subjects: Astronomy and Astrophysics; Antarctic; The Antarctic; Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.3389/fspas.2023.1198739; https://www.frontiersin.org/articles/10.3389/fspas.2023.1198739/full

This brief report examines the ground-based total electron content (TEC) in Asian sector during August–October 2019, covering the period of a stratosphere sudden warming (SSW) occurred in Antarctica. The analysis reveals pronounced ionospheric day-to-day variability with distinct periodicities. The most dominant and long-lasting periodicities are quasi-10 days and quasi 14-day during September and October, while a quasi 6-day also present in September. The 10-day and 6-day TEC oscillations were attributed by previous studies solely to the Antarctic SSW while assuming negligible geomagnetic effects. By comparing co-located ground mesospheric wind observations, along with the interplanetary electric field (IEF) and geomagnetic activity (Kp index), we demonstrate that the quasi 14-day oscillation is mainly driven by low-level geomagnetic activities, while quasi-6 days oscillation is driven by mesospheric wind changes during the SSW. The 10-day oscillation, on the other hand, is driven by both IEF and mesospheric wind in September, but by IEF in October. These results demonstrate that low-level geomagnetic activities traditionally classified as “quiet conditions” can induce significant day-to-day oscillations in TEC, and their impacts should not be ignored when studying meteorological (e.g., SSWs) impacts on the ionosphere.