Observation of an Intriguing Equatorial Plasma Bubble Event Over Indian Sector

Abstract

Ionospheric irregularities are frequently generated at F-region during post-sunset period over the equator through Rayleigh-Taylor (RT) instability. RT instability gives rise to a hierarchy of irregularities of scale sizes from few cm to hundreds of km whose signatures are termed as Equatorial Spread-F in ionograms or plasma plumes in radars (e.g., Kelley, 1989;Kelley et al., 2011;Patra et al., 2014). In optical data, they are named as Equatorial Plasma Bubbles (EPBs) and are manifestation of large-scale plasma irregularities. EPBs grow nonlinearly at the equator and simultaneously get mapped to low latitudes along the magnetic field lines (e.g., Makela & Otsuka, 2011). OI 630.0 nm airglow imaging captures the nightglow emission which arises from the dissociative recombination of O 2 + with electron and has peak emission altitude at ∼250 km (e.g., Sahai et al., 2006). The dark, field aligned bands observed in the OI 630 nm images are manifestation of electron density bite outs representing the occurrence of EPBs. Such structures have been previously imaged at low latitude stations using optical techniques (e.g., Martinis et al., 2018;Taori et al., 2013).Many researchers have studied the dynamics of EPBs in the context of their zonal drifts, occurrence statistics, morphological evolution etc (e.g.,