Investigation of Spatiotemporal Morphology of Plasma Bubbles Based on EAR Observations

Spatiotemporal characteristics of equatorial plasma bubble (EPB) have been studied based on Equatorial Atmosphere Radar (EAR) fan sector observations from Kototabang. EPBs were characterized as either locally generated (whose genesis and subsequent evolution was observed in the fan sector maps) or drifted type (which drifted into fan sector scans from west). Investigation of the radar echo spectral width indicated that the drifted EPB could be less evolving type. Height of the F layer in the postsunset period over Kototabang and Chumphon were examined in the two types. Average peak h′F was higher in locally generated EPB cases than in drifted EPB cases (by ~25 km), which is also found to be statistically significant. This scenario has been visualized in terms of a standing large-scale wave structure (LSWS) whose phase determine whether EPB will be seen evolving over EAR or drifted from a western longitude. Furthermore, low-latitude sporadic E (E_s) variabilities in the two cases were also examined. E_s indicated an inverse relation with the peak h′F (which depends on crest/trough of LSWS). These results have been discussed in the light of earlier works on spatial morphology of EPB clusters, particularly in context to the possible generation mechanism of LSWS by the spatial inhomogeneity in the low-latitude E region conductivity. Lesser occurrence of low-latitude E_s in locally generated EPB cases also signifies the vital role of E region conductivity on Rayleigh-Taylor instability. These results highlight a need for networked spatial observation of low-latitude E_s.