Enhanced ionospheric plasma bubble generation in more active ITCZ

Abstract

A close link between the atmospheric Intertropical Convergence Zone (ITCZ) and ionospheric plasma bubble has been proposed since the last century. But this relationship has often appeared to be less than convincing due to the simultaneous roles played by several other factors in shaping the global distribution of ionospheric bubbles. From simultaneous collaborative radar multibeam steering measurements at Kototabang (0.2°S, 100.3°E) and Sanya (18.4°N, 109.6°E), conducted during September–October of 2012 and 2013, we find that the total numbers of nights with bubble (i.e., occurrence rates) at the two closely located longitudes (Kototabang and Sanya) are comparable. But interestingly, the total number of nights with locally generated bubble (i.e., generation rate) over Kototabang is clearly more than that over Sanya. Further analysis reveals that a more active ITCZ is situated around the longitude of Kototabang. We surmise that the enhanced ionospheric bubble generation at Kototabang longitude could be caused by a higher gravity wave activity associated with the more active ITCZ.

Unseasonal development of post-sunset F-region irregularities over Southeast Asia on 28 July 2014: 1. Forcing from above?

“…Atmospheric gravity waves from the troposphere are also suspected to influence the F-region vertical plasma drift (Li et al 2016) and play a role in the seeding and development of EPBs (e.g., McClure et al 1998;Tsunoda 2010a, b); atmospheric gravity waves therefore represent another form of forcing from below. One would expect that atmospheric gravity waves that seed EPBs would originate from a local source, whereas tides or planetary waves would be expected to exhibit larger scale, perhaps even global, effects.…”

Nightside ULF Waves Observed in the Topside Ionosphere by the DEMETER Satellite

“…Su et al () studied the correlation between distributions between deep convective clouds in the ITCZ and plasma irregularities, and results indicated that correlations only exist in South American and African sectors. Li et al () suggested that enhanced plasma irregularity generation is caused by gravity waves in the more active ITCZ. Dramatic effects may occur in the ITCZ; Parrot et al () presented that maximal occurrence of spectacular emission events observed by the DEMETER occurred over the Atlantic which also lies in the ITCZ.…”

LSWS linked with the low‐latitude Es and its implications for the growth of the R‐T instability

“…Various investigations have revealed the presence of large-scale longitudinal modulation of the ESF [eg., Kelley et al, 1981;Tsunoda, 1983]. It has been found that the equatorial plasma bubble does not occur continuously but has a longitudinal modulation much greater than the longitudinal dimension of an individual bubble [Tsunoda et al, 2011;Tulasi Ram et al, 2012;Li et al, 2013;Tulasi Ram et al, 2014;Tsunoda, 2015;Li et al, 2016]. This longitudinal modulation has been found to be related with the large-scale wave structure (LSWS) found in the evening F layer.…”