Multi-instrument investigation of troposphere-ionosphere coupling and the role of gravity waves in the formation of equatorial plasma bubble

Abstract

Present study investigates the role of gravity waves in the generation of equatorial plasma bubbles (EPBs) during geomagnetic quiet conditions using co-located observations from Gadanki (13.5oN, 79.2° E) an all sky airglow imager, Gadanki Ionospheric Radar Interferometer (GIRI) and Ionosonde observations from Tirunelveli (8.7° N, 77.8° E). To avoid any changes occurring in the background ionosphere, four consecutive nights of observation during 03–06 February 2014 is used. Out of these four nights, three nights (i.e., 03, 05 and 06 February 2014) exhibit occurrence of EPBs in the OI 630 nm airglow emission and radar plumes and there is no bubble occurrence during one night, though the ionospheric peak altitude (h′F) value is more than 350 km in all these nights. During these four nights the structures observed in the E-region drifts and gravity waves noted in the mesospheric OH emissions are analyzed. It is found that there are common periodic oscillations in the OH peak emission altitude and E-region in three nights (03, 04 and 05 February 2014). The mesospheric gravity wave structures are ray traced to their potential sources in the lower atmosphere and also for the possibility of their propagation to the E-region. Our results suggest that apart from horizontal wavelength and amplitudes, the propagation angle of gravity wave may also be important for seeding of the Rayleigh-Taylor (R-T) instability. Thus, it gives an insight about the role of lower – middle and upper atmospheric coupling on the occurrence of the noted EPBs.