Madden-Julian Oscillation Modulation of Ionospheric Tides: Insights from COSMIC-2 Observations (2020-2022)

The Madden-Julian Oscillation (MJO), an eastward moving disturbance typically occurring every 30-96 days in tropical precipitation, is the dominant mode of intraseasonal variability in tropical convection and circulation. In this paper, we examine how atmospheric tides map the MJO into the space weather of F-region ionosphere, as it facilitates an enhanced understanding of the relative seasonal and interannual fluctuations resulting from the propagation of lower atmospheric waves. Previous studies already showed a strong MJO signal in migrating and non-migrating temperature tides in the mesosphere/lower thermosphere. The mechanism is as follows: The MJO changes global-scale waves through convective forcing modulation, stratospheric gravity waves (GW) drag, and mean winds, depending on the season, MJO magnitude, and phase. The MJO response in ionospheric tides is likely due to either E-region dynamo modulation or direct tidal upward propagation with corresponding changes in thermospheric composition. The availability of ionospheric data from the COSMIC-2 satellite constellation allows us, for the first time, to explore the ionosphere's response to MJO. The day-to-day tidal wave spectrum is extracted from COSMIC-2 hourly GIS data in the altitude range from 120 km to 720 km for Jan 2020- Dec 2022. Further applying Hovmoeller analysis and typical MJO definition, which examines their longitudinal and temporal evolution within the 30-96-day period range and zonal wavenumbers 1-5, the MJO pattern in ionospheric tides is retrieved. We present results for three tidal components, DW1, DE3, and DE2, and discuss their relevance of ionospheric space weather predictability on intraseasonal timescales.