Collaborative Research: CEDAR--Three-dimensional Large Electron Density Gradients at Mid-latitudes from a TEC-based Ionospheric Data Assimilation system (TIDAS)

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This project will investigate two significant and sometimes concurrent phenomena in the mid-latitude ionosphere, which is a region of atmosphere with relatively higher concentration of charged particles from about 60 km to 1000 km altitude. These two phenomena are called storm-enhanced density (SED) plumes and the main ionospheric trough. They refer to large spatial variations in electron density (Ne) in the ionosphere, often associated with geospace storms which are disturbances in the Earth’s magnetic fields due to sudden changes in solar energy input. These large electron density gradients are known for imposing substantial and detrimental space weather effects on navigation and communication systems.The overall goal of this project is to characterize these ionospheric density gradients in a three-dimensional (3-D) domain, and to understand the fundamental physical processes responsible for gradient formation and development. This will be accomplished by conducting three tasks: (a) creation of a 3-D electron density profile database for moderate-to-major geospace storms since 2006, using a data assimilation system to produce the database; (b) construction of the first regional 3-D empirical models of SED plumes and the main trough, containing information on their detailed spatial-temporal variations and geophysical dependence; and (c) through a combined physics-based and data-driven modeling approach, advancing understanding of SED and main trough mechanisms, including relative roles of electrodynamics and neutral dynamics as well as associated ionosphere-thermosphere coupling processes.Scientific studies [Tasks (b) and (c)] will investigate SED and trough statistical morphology, focusing on their storm-time inter-relationship, geophysical dependence, and variability of the driving processes. These processes and their roles in the formation and evolution of gradients will be investigated using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM). A realistic initial state specification of global Ne with SED and trough, provided by data assimilation and empirical models [Tasks (a) and (b)], will feed into TIEGCM at each time step for the gradient simulation. These processes will then be estimated using the Ensemble Kalman filter algorithm and understanding of their significant storm-time variability can be addressed. This project targets the important community challenge of understanding extremely dynamic ionospheric density gradients in a 3-D domain. SED and trough characteristics will be investigated not only in the Total Electron Content (TEC) but also in NmF2 (F2 region peak electron density), hmF2 (height of the peak electron density in F2 region), and full Ne profiles. Furthermore, through use of TIDAS (TEC-based Ionospheric Data Assimilation System) results as initial conditions for first-principle model simulations, this study addresses significant and unique variability of physical driving processes of the gradients in a novel way through comparative analysis of the simulations and observations. Several unique and open-access community data products will be generated, including storm-time 3-D ionospheric dataset since 2006. It will lay the foundation for future efforts targeting regular ionospheric 3-D specification in a synchronized fashion with the existing Madrigal TEC database, serving a broad research community. Community empirical models of SED and the trough will be produced that directly address space weather application needs in gradient specification. Undergraduate students will be involved with data analysis and simulation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.