On the role of vertical electron density gradients in the generation of type II irregularities associated with blanketing ES (ESb) during counter equatorial electrojet events: A case study

The characteristics of different types of Sporadic E (E S ) layers and the associated plasma density irregularities over the magnetic equator have been studied in a campaign mode using VHF backscatter radar, digital ionosonde, and ground magnetometer data from Trivandrum (dip latitude 0.5°N, geographic latitude 8.5°N, geographic longitude 77°E), India. The presence of blanketing type E S (E Sb ) in the ionograms with varying intensity and duration were observed in association with afternoon Counter Equatorial Electrojet (CEEJ) events. E Sb was associated with intense backscatter returns and with either very low zonal electric field and/or with distortions present in the altitude profile of the drift velocity of the type II irregularities. The results of the coordinated study indicate the possible role of vertical electron density gradients in E Sb layers in addition to providing evidence for the local winds to be responsible for the vertical gradients themselves.