Day-to-day variability of the semidiurnal tide in the F-region ionosphere from COSMIC-2 in response to polar vortex strength variations

COSMIC-2 F-region electron densities from the hourly GIS data open a new window of opportunity to understand how weather-like variations from the lower atmosphere impact the global space weather of the ionosphere from a constellation point of view. A new capability to diagnose tides on a day-by-day basis shows a surprisingly close match of the F-region semidiurnal tide in both hemispheres with daily variations in the strength of the polar vortex during Sudden Stratospheric Warmings (SSW), consistent with very recent modeling studies that connected mesosphere/lower thermosphere semidiurnal tidal variability with daily variations in the Northern Annual Mode. Polar vortex wind vacillations on the order of 5-10 m/s during the January 2021 SSW cause electron density semidiurnal tidal amplitudes to change by a factor of two within a few days. The comparison with 35-day running mean tidal diagnostics from ICON supports E-region dynamo modulation as the leading coupling mechanism while thermospheric composition can be ruled out through diagnostics of GOLD data. The broader implications of the present work is that the day-to-day variability in the COSMIC-2 ionospheric tides, which is not limited to SSW events, can potentially be connected to the dynamics of the troposphere and stratosphere that can be predicted several days or weeks in advance (like the Northern Annual Mode or the Madden-Julian Oscillation).