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

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.

Automated summary

This report examines the ground-based total electron content (TEC) in Asian sector during August-October 2019, with a focus on the period of a stratosphere sudden warming (SSW) occurred in Antarctica. The study reveals pronounced ionospheric day-to-day variability with distinct periodicities, including quasi-10 day, quasi-14 day, and quasi-6 day oscillations. The findings demonstrate that low-level geomagnetic activities and mesospheric wind changes during the SSW have significant impacts on TEC, which should not be ignored when studying meteorological effects on the ionosphere.