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Ionospheric Studies

isr exploring total electron content, geomagnetic storm effects, and other phenomena


Magnetosphere-Ionosphere (MI) coupling

Flow of energy between the magnetosphere and ionosphere is known to be the dominant source of ionospheric density enhancement at auroral and sub-auroral latitudes. This effect expands to lower latitudes particularly during geomagnetic storms. Studies suggested that the ionospheric plasma is transported sunward and poleward from a source region at middle and low latitudes in the afternoon sector, which is associated with the large-scale enhancement of the ionospheric convection electric field during disturbed geomagnetic conditions, forming a latitudinally narrow region of storm-enhanced plasma density (SED) that convects  sunward extending toward higher latitudes. It is well known that these SED plumes are associated with the erosion of the outer plasmasphere. However, the rates of SED plume formation difference at different longitudinal sectors are still not fully understood. We have been utilizing data from multi-instrument observations and making significant progress toward this effort. 


Equatorial Electrodynamics

It is now well documented that ionospheric and plasmaspheric density irregularities and gradients are the prime candidate for the failure of our navigation and communication systems especially during magnetically active periods. Despite much progress in the study of ionospheric and plasmaspheric density structure and dynamics in the last decade, there are many gaps in our global understanding of the fundamental electrodynamics that governs equatorial ionospheric density irregularities and gradients. The uneven distribution of ground-based instruments has been the main barrier that hinders our ability to obtain a global understanding of the dynamics and structures of the ionosphere. Most of ground-based instruments are located in dense regional arrays in North America, Europe, Asia, and recently in South America. However in Africa, where some of the most intense ionospheric density irregularities occur, observations of the state of ionospheric plasma and its driving electrodynamics are not possible due to lack of ground-based instruments. In order to have a complete global understanding of equatorial ionosphere motions, we deployed AMBER magnetometer arrays in four African countries and also proposed ACORN GPS receivers’ network to be deployed in Africa.   

ACORN Project in Africa

The proposed ACORN GPS network will play a vital role in the effort to advance global understanding of the dynamics and structure of the ionospheric density irregularities. The prime objective of ACORN is to monitor the complex and extreme state of disturbance that occurs in the magnetic-equatorial ionosphere nearly every day after sunset as has been observed by satellite observations, and the electrodynamics of the plasma density that creates the proper conditions to initiate plasma turbulence. Satellite observations show unique equatorial ionospheric structures only in the African sector, though these have not been confirmed, validated or studied in detail by ground-based observations due to lack of suitable ground-based instrumentation in the region.


Ground- and Space-based Tomography
The TEC measurements by themselves are just a collection of line integrals of the free electron density and not maps of the electron density distribution or structure. The dramatically growing number of GPS receivers on the ground and onboard Low-Earth-Orbit (LEO) satellites offers an excellent opportunity for remote sensing and monitoring of the ionospheric and plasmaspheric density structure using tomographic reconstruction technique. This allows us to clearly quantify M-I coupling dynamics, as well as confirm the long-standing conjecture that the mid-latitude trough and plasmapause are on the same field line. We have been performing in imaging F-region ionospheric and topside ionospheric and plasmaspheric density structures and dynamics by applying tomographic inversion techniques to ground- and space-based observations, respectively.

Point of Contact for this project is Endawoke Yizengaw.