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DECEA - Dynamical and Electro-dynamical Coupling of Equatorial Atmosphere

The upper regions of the Earth's atmosphere (namely, the thermosphere and the coexisting ionosphere) are strongly coupled to the lower and middle atmosphere by means of chemical, dynamical and electrodynamical processes. The observed influence of the upward propagating gravity and planetary-scale waves and atmospheric tides on the thermosphere and ionosphere is an example of dynamical coupling. The giant global electrical circuit (GEC) linking the lower atmosphere with the ionosphere and the magnetosphere provides an adequate mechanism for the electrodynamical coupling. Both the dynamics and electrodynamics in the equatorial regions differ substantially from those at higher latitudes. Atmospheric dynamics in the equatorial region is more complex considering the absence of the Coriolis force that results in the breakdown of the concept of geostrophic flow.

The uniqueness of the electrodynamics of the equatorial region stems from the horizontality of the ambient magnetic field resulting in a diversity of phenomena such as the equatorial electrojet (EEJ), the equatorial spread-F (ESF), the plasma fountain leading to equatorial ionization (EIA) and neutral (NA) anomalies, etc. The EEJ manifests itself in the geomagnetic field variations and the same electric field driver controls the dynamics of the F region of the ionosphere up to the latitude of the crest of the EIA. A variety of instabilities is driven by the electrodynamics of E and F regions, which are studied with ground-based ionosonde, coherent radars, airglow instruments, low-Earth orbiting satellites and also through radio wave scintillations.

With a suite of radio and optical remote sensing techniques, this programme aims to probe the coupled neutral and plasma environments of the upper atmosphere. The focus will be on addressing some fundamental questions like what are the major drivers of the large scale electric fields and currents at low latitudes, how does a plasma bubble develop, evolve and decay, what are the ambient conditions required for the onset of the plasma density irregularities, what are the sources (both quiet and disturbed times) of the geophysical variability in the day-to-day time scales observed at upper atmospheric altitudes, etc. Studies are proposed to address the forcing of the atmosphere-ionosphere system from below in the form of mesoscale convective systems, thunderstorms, lightning discharges, gravity waves, tropical cyclones, etc. and their interrelationships.