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The Earth's low- and mid-latitude ionosphere hosts a number of complex phenomena resulting from the coupled dynamics of thermospheric winds, ionospheric plasma, electric fields and ionospheric currents, under the influence of Earth’s magnetic field. This region is exposed to constantly varying conditions of both terrestrial and space weather, giving rise to considerable day-today variability in the coupled thermosphere and ionosphere system. In spite of significant progress in the development of our understanding of diurnal and seasonal variations of low- and mid-latitude electrodynamical processes in recent decades, little progress has been made in terms of fully understanding and predicting their observed longitudinal variations and day-to-day variability. 

The project's objective is to develop a comprehensive inversion and data assimilation approach tailored specifically to the problem of mid- and low-latitude electrodynamics, in order to improve our understanding of the origins of the observed longitudinal and day-to-day variability in plasma distribution, plasma drifts, and ionospheric currents. Specific science questions addressed include: (1) What are the causes of the observed day-to-day variability of daytime large scale low- and mid-latitude phenomena, including equatorial plasma drifts, EIA, EEJ and Sq currents, along with its longitudinal dependency for different seasons? To what degree is the EEJ and Counter Electrojet variability related to the Sq variability; (2) To what extent is the longitudinal dependence controlled by the geometry and magnitude of geomagnetic fields, and by atmospheric tides originating from the lower atmosphere?; (3) What are the relative contributions of the penetration and disturbance electric fields associated with space weather drivers and of tidal and planetary waves associated with terrestrial weather drivers to the observed day-to-day variability of plasma distribution, plasma drifts, and ionospheric currents? 

• Funding sources:  $250K (2017-2020) from NSF CEDAR Program
• PI: Tomoko Matsup (ÃÛÌÒ´«Ã½Æƽâ°æÏÂÔØ)
• Collaborators:  NCAR, UT Dallas
• Societal relevance: The project will help accurately determinatine a global, instantaneous distribution of TEC and plasma drifts. Radio wave scintillations are often co-located with strong gradients in TEC and plasma drifts are known to be an important factor for the evolution of plasma irregularities causing scintillations that affects communication positioning, navigation, and positioning.