Abstract:
Using the equatorial electrojet (EEJ)-induced surface magnetic field and total electron content
(TEC) measurements, we investigated the impact of the sudden stratospheric warming (SSW) of January
2009 on the equatorial electrodynamics and low-latitude ionosphere over the Indian longitudes. Results
indicate that the intensity of EEJ and the TEC over low latitudes (extending up to 30°N) exhibit significant
perturbations during and after the SSW peak. One of the interesting features is the deviation of EEJ and TEC
from the normal quiet time behavior well before the onset of the SSW. This is found to coincide with the
beginning of enhanced planetary wave (PW) activity over high latitudes. The substantial amplification of the
semidiurnal perturbation after the SSW peak is seen to be coinciding with the onset of new and full moons.
The response of TEC to SSW is found to be latitude dependent as the near-equatorial (NE) stations show the
semidiurnal perturbation only after the SSW peak. Another notable feature is the presence of reduced
ionization in the night sector over the NE and low-latitude regions, appearing as an “ionization hole,” well
after the SSW peak. The investigation revealed the existence of a quasi 16 day wave in the TEC over low
latitudes similar to the one present in the EEJ strength. These results have been discussed in the light of
changes in the dynamical background because of enhanced PW activity during SSW, which creates favorable
conditions for the amplification of lunar tides, and their subsequent interaction with the lower thermospheric
tidal fields.
