Abstract:
A double‐peak structure in the peak height of ionospheric F2 layer around ±10o geomagnetic
latitudes similar to the equatorial ionization anomaly was recently reported. This unique feature was
referred as the equatorial height anomaly (EHA). In the present paper, a simulation study is carried out
using the data‐driven artificial neural network‐based two‐dimensional ionospheric model (ANNIM‐2D) and
the physics‐based thermosphere‐ionosphere‐electrodynamics general circulation model (TIEGCM) to
understand the local time and latitudinal variation of EHA during the main phase of St. Patrick's Day
geomagnetic storm. Both the ANNIM‐2D and TIEGCM consistently show pronounced EHA during the
main phase of the geomagnetic storm. Further, the local time of EHA development on the storm day is much
earlier (nearly 2 hr) than the quiet time over Brazilian sector (90°W). The TIEGCM simulation revealed that
the storm time enhancement of the equatorial fountain associated with the enhanced equatorial zonal
electric field is the main controlling factor for the pronounced EHA during the main phase. The storm time
meridional neutral winds positively contribute to the development of EHA. This study revealed the direct
manifestation of the storm time‐enhanced plasma fountain on the EHA.
