  The paper presents an assessment of the performances of the global empirical
models: International Reference Ionosphere (IRI)-2016 and the NeQuick2 model
derived ionospheric Total Electron Content (TEC) with respect to the Navigation
with Indian Constellation (NavIC)/ Indian Regional Navigation Satellite
System(IRNSS) estimated TEC under geomagnetic storm conditions. The present
study is carried out over Indore (Geographic: 22.52$^{\circ}$N 75.92$^{\circ}$E
and Magnetic Dip: 32.23$^{\circ}$N, located close to the northern crest of the
Equatorial Ionization Anomaly (EIA) region of the Indian sector). Analysis has
been performed for an intense storm (September 6-10, 2017), a moderate storm
(September 26-30, 2017) and a mild storm (January 17-21, 2018) that fall in the
declining phase of the present solar cycle. It is observed that both IRI-2016
and NeQuick2 derived TEC are underestimates when compared with the observed TEC
from NavIC and therefore fail to predict storm time changes in TEC over this
region and requires real data inclusion from NavIC for better prediction over
the variable Indian longitude sector.
