Equatorial plasma bubble seeding by MSTIDs in the ionosphere

Hisao Takahashi,Mangalathayil Ali Abdu,Kazuo Shiokawa,Yuichi Otsuka,Cosme Alexandre Oliveira Barros Figueiredo,Diego Barros,Cristiano Max Wrasse

doi:10.1186/s40645-018-0189-2

Abstract

Occurrences of equatorial plasma bubbles (EPBs) and medium-scale traveling ionospheric disturbances (MSTIDs) were studied using GPS satellite data-based total electron content mapping, ionograms, and 630 nm all-sky airglow images observed over the South American continent during the period of 2014–2015. In many cases, we observed a close relationship between the inter-bubble distance and the horizontal wavelength of the MSTIDs. The MSTIDs followed by EPBs occurred primarily in the afternoon to evening period under strong tropospheric convective activities (cold fronts and/or intertropical convergence zones). The close relationship between EPBs and MSTIDs suggests that MSTIDs could be one of the seeding sources of EPBs.

Highlights

Equatorial plasma bubbles (EPBs) are a consequence of the development of equatorial ionospheric irregularities under the condition of the Rayleigh–Taylor instability (RTI)
One can recognize that, along the geomagnetic equator line, total electron content (TEC) depletion extended from 35° W to 55° W. This is the trough of the post-sunset equatorial ionization anomaly (PS-EIA), which is caused by F-layer plasma uplift due to an increase in the zonal electric field, known as pre-reversal enhancement of the electric field (PRE), during the sunset period
Note that the Total electron content map (TECMap) (Fig. 1) shows periodic TEC decreasing along the magnetic equator, some of which extended toward the southeast as highlighted by the elliptical circles numbered 1, 2, and 3

Summary

Introduction

Equatorial plasma bubbles (EPBs) are a consequence of the development of equatorial ionospheric irregularities under the condition of the Rayleigh–Taylor instability (RTI). Many previous studies have highlighted possible seeding processes, such as contributions of atmospheric gravity waves in the ionosphere (Rottger 1973; Singh et al 1997), the passage of the solar terminator (Tulasi Ram et al 2014), and medium-scale traveling ionospheric disturbances (MSTIDs) (Taori et al 2015). Vertical oscillations of the longitudinal waves increase toward the evening side and may accelerate F-layer uplifting, For the RTI condition scenario, the development and physical characteristics of EPBs have been extensively studied and discussed and there exists some common knowledge (e.g., Abdu 2001). Singh et al (1997) reported a possible mechanism for the periodic ion density perturbation caused by gravity waves, which develop into plasma bubbles. Abdu et al (2015) discussed atmospheric gravity waves in the ionosphere as a potential source to excite plasma bubbles

Results

Discussion

Conclusion