Decay of 3‐m‐scale ionospheric irregularities associated with a plasma bubble observed with the Equatorial Atmosphere Radar

We investigated the decay processes of 3‐m‐scale ionospheric irregularities associated with plasma bubbles by multi‐instrument observations. The observations were made using the Equatorial Atmosphere Radar (EAR), a 630‐nm airglow imager, and ionosondes. The EAR's electronic beam steering capability allowed us to see the temporal evolution of 3‐m‐scale irregularities associated with plasma bubbles in two‐dimensional views. Around midnight on 28 and 31 March 2006, the EAR detected plasma bubbles that drifted into its field of view. When their eastward drift motion slowed and they finally stopped moving eastward, the 3‐m‐scale irregularities decayed. These results suggest that instability driven by the eastward neutral wind kept the 3‐m‐scale irregularities in matured plasma bubbles, which are in the well‐developed stage, active for several hours after sunset. The stagnated plasma bubbles drifted downward with the ambient westward electric field. This drift resulted in the backscatter echo patterns seen in the range‐time‐intensity (RTI) plots which look like those associated with mid‐latitude plumes.