Coincident Airglow, VHF Radar, and Ionosonde Observations of Electrified Medium‐Scale Traveling Ionospheric Disturbances in the Equatorial Latitudes

Abstract

The occurrence of late night spread F in the low and equatorial latitude regions during solar minimum is not properly understood. Radar observations have revealed occurrence of postmidnight echoes at low and equatorial latitudes during solar minimum periods. This work discusses the coordinated airglow, VHF radar, and ionosonde observations of nighttime electrified medium‐scale traveling ionospheric disturbances (EMSTIDs) made from the low and equatorial latitude Indian region. Two nights of observations are discussed in detail in which EMSTIDs are seen to coexist with spread F in ionograms and VHF backscatter. These observations reveal that the EMSTIDs propagate to latitudes very close to dip equator at times and they can be responsible for a reasonable portion of the postmidnight radar echoes and spread F events observed at low and equatorial latitudes during low solar activity period.