Day-to-day variability of the semidiurnal tide in the F-region
ionosphere during the January 2021 SSW from COSMIC-2 and ICON
Abstract
The semidiurnal tidal spectrum in the F-region ionosphere obtained from
hourly COSMIC-2 Global Ionospheric Specification data assimilation is
greatly (>50%) enhanced during the January 2021 Sudden
Stratospheric Warming (SSW). Moreover, the semidiurnal migrating tidal
response in topside electron densities closely follows the day-to-day
changes of the 10 hPa, 60oN zonal wind from MERRA-2
during the SSW. The response is similar in the northern and southern
crests of the Equatorial Ionization Anomaly (EIA) but persists towards
higher magnetic latitudes and the EIA trough. A slight phase shift
towards earlier local times is consistent with theoretical expectations
of an E-region dynamo driving and agrees with semidiurnal tidal
diagnostics of MIGHTI/ICON zonal winds at 105 km. The COSMIC-2 data are
the first data set to resolve the tidal weather of the ionosphere on a
day-to-day basis and, therefore, provide a new perspective on space
weather variability driven by lower and middle atmosphere dynamics.