Longitudinally-Dependent Low-Latitude Ionospheric Disturbances Linked to
the Antarctic Sudden Stratospheric Warming of September 2019
Abstract
The strongest Southern Hemisphere minor sudden stratospheric warming
(SSW) in the last 40 years occurred in September 2019 and resulted in
unprecedented weakening of the stratospheric polar vortex. Ionospheric
total electron content (TEC) observations are used to provide an
overview of statistically significant anomalies in the low-latitude
ionosphere during this event. Quasi-semidiurnal perturbations of TEC are
observed in response to the SSW, similar to those seen during Northern
Hemisphere SSWs. Analysis indicates the existence of quasi-periodic
oscillations in TEC in the crests of the equatorial ionization anomaly,
with strong 5-6 day and 2-3 day periodicities. Ionospheric anomalies
from the combined effects of multiple mechanisms exceed a factor of 2,
comparable to the strongest anomalies associated with Northern
Hemisphere SSWs. These results also indicate, for the first time, a
remarkable longitudinal variation in the character and magnitude of
variations that could be related to a modulation of the non-migrating
diurnal tide.