Research Theme: Morphology of Earth’s Ionosphere-Thermosphere System

Rationale of my research: Earth’s ionosphere over the magnetic equator is characterized by the presence of plasma irregularities during certain nights, referred as equatorial spread F (ESF). These irregular structures can rigorously affect numerous applications including the positioning and navigation in Global Positioning System, communication and remote sensing etc. The fundamental features of the processes responsible for the generation of these irregularities are not completely understood. The complexity lies in the fact that so many parameters are to be considered simultaneously. It has been reported that even under the identical background conditions, there is no guarantee on the occurrence of ESF. The night-to-night variability of this phenomenon provides evidence about the coupling of different atmospheric processes as well as the complexity involved in predicting it. The current understanding in the field of ionospheric research is not sufficient to account completely, for the variability of these processes. The major reason is the lack of detailed understanding regarding the coupling existing among different factors. This points to the need for systematic studies to bring out the role various parameters like the wind system, gravity waves and planetary waves, ionospheric conductivity, lower atmospheric-, thermosphere-, solar- forcing etc as well as their interdependencies in a quantitative manner as well as to develop prediction schemes for irregularities and scintillations. Thus while these studies will cater to the scientific curiosity, they will at the same time aid in forecasting the status of the ionosphere which is extremely important for mitigating communication and navigation outages A comprehensive analysis on the various of solar, atmospheric-, thermospheric factors inclusive of plasma drifts, plasma fountain, atmospheric waves, neutral density are need to be established for the complete understanding.

Details of my research work: The characteristics and climatology of the Gravity Wave induced Travelling Ionospheric Disturbances (GW-TIDs) in the ionosphere and their quantitative role in modulating the day-to-day variability of Equatorial Spread F are addressed (ASR, 2016; JASTP, 2017). It is revealed that the amplitude of the GW-TID is a very critical parameter which decides, whether or not Equatorial Spread F would occur on a given day and that, this threshold level of seed perturbation amplitude required on a given day decreases as the post sunset height of the F- layer increases (JGR, 2017). The role of neutral density in modulating the threshold curve amplitude of the seed perturbations (gravity wave induced perturbations) for Equatorial Spread F initiation was addressed (JGR, 2018a).The response time of Equatorial Ionization Anomaly (EIA) crest ionization and its location, its seasonal and solar activity variability, the causative mechanisms, linkage between the EIA delay and the Equatorial Spread F, for the days when the F-layer base is in the neutral dynamical domain were explored (JGR, 2018b). Empirical models were generated for hind-casting the ESF events for the days belonging to the electrodynamics- domain (JGR, 2018c). The effect of the time of evening zonal drift reversal in F- region on the post sunset ionosphere is established, for the first time (JASTP, 2020). The seasonal and solar activity variation of the post sunset F- region zonal plasma drift, at the magnetic equatorial region is analyzed for magnetically quiet conditions and its linkage with the plasma irregularities are addressed (ASR, 2020). Role of the planetary planetary waves in the off-equatorial E- region and the subsequent modulation of F region parameters via the magnetic field lines were examined (JGR, 2020). Effect of the near sunset EIA crest magnitude on modulating the post sunset irregularities on a night-to-night basis is extracted (ASR, 2021). I have worked on the testing and analysis on the Ionization Density and Electric-field Analyzer (IDEA) payload on board the Polar Satellite 4 (PS4) stage provided electron density and electric field information at the F region altitudes (JASTP, 2019).

Significance of my research work: While my studies will cater to the scientific curiosity, they will at the same time aid in forecasting the status of the ionosphere which is extremely important for mitigating communication and navigation outages.

Publications: 12 Publications in international peer-reviewed journals.