On the altitude of initiation of the gradient drift waves at different longitude sectors in the vicinity of the dip equator

• Longitudinal variation in the altitude of initiation (AOI) of E region gradient drift (GD) waves.
• AOI of GD waves is inversely proportional to the square of geomagnetic field strength.
• Increased growth rate of GD waves over Indian zone by a factor of 2.4.

In order to understand the variation in the altitudes of initiation (haoihaoi) of E region gradient drift (GD) waves at different longitude sectors in the vicinity of the dip equator, the linear growth rate expression was examined. This revealed that the growth rate of the primary GD waves in an altitude region of 85–93 km depends on the square of the geomagnetic field strength (B  ). This is shown to explain the lower haoihaoi of GD waves over Indian longitude vis-a-vis American longitudes. The available observations on the GD waves from different longitude sectors reveal that the haoihaoi is inversely proportional to B2.