  Study of the dynamic nature of low-latitude ionosphere during geomagnetically
disturbed conditions, especially in the EIA and the magnetic equatorial regions
are vital for understanding the underlying physics as well as for mitigating
space weather hazards on the sophisticated technological systems essential for
human civilization. An important aspect of the space weather studies is the
thorough understanding of coupling between the solar wind and the terrestrial
magnetosphere-ionosphere system and subsequent influence on the low-latitude
ionosphere. This paper presents an effort to understand the influence of actual
values of the north-south component of Interplanetary Magnetic Field (IMF,
$B_z$) on the vertical plasma drifts at a location near the EIA and the
geomagnetic equator. The strong storm event of October 13, 2016, falling in the
descending phase of solar cycle 24, has been taken up as a case study.
Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM)
simulation runs have been performed under two scenarios: first when no coupling
is present (IMF $B_z$ = 0 nT) and second when actual observations of the values
of IMF $B_z$ is given as inputs to the model. Observations show when actual
data is fed to the model, there is significant shift of the vertical drift
towards westward, while there is an increase in the peak value of the westward
drift after the pre-reversal enhancement. This study is an initial effort to
understand the variations in low-latitude plasma motions during the main phase
of strong geomagnetic storms. This initial work will be followed up with
understanding the global plasma drift variations under the influence of other
components of the IMF near the EIA and the dip equatorial regions.
