An Ionospheric Forecasting System

B. Khattatov, M. Murphy, M. Gnedin, B. Cruickshank, J. Boisvert, J. Sheffel, V. Jayaraman,T. Fuller-Rowell

Abstract:	This paper describes an operational system sponsored by the US Air Force for generating and distributing near real-time three-dimensional ionospheric electron densities and corresponding GPS propagation delays. The system adapts technologies developed and routinely used for operational weather forecasting in order to nowcast and forecast ionospheric conditions. It consists of two parts: a first-principles numerical model of the ionosphere and a data assimilation component. The core ionospheric model solves plasma dynamics and composition equations governing evolution of density, velocity and temperature for 7 ion species on a fixed global three-dimensional grid in magnetic coordinates. It uses a realistic model of the Earth´s magnetic field and solar indices obtained in real time from the NOAA Space Environment Center. At the present time the model computes real-time ion and electron densities at a grid of more than one million points. Higher resolutions are anticipated in the future. While the core model is capable of delivering realistic results, its accuracy can be significantly improved by employing a special set of numerical techniques known as data assimilation. These techniques originated in and are currently used for numerical weather forecasting. The core ionospheric model is continuously fed data from a network of reference GPS ground stations. This improves both the nowcast and the forecast. The system also computes uncertainties of the forecast and nowcast via a large-scale suboptimal Kalman filter. We believe that given advances in computing power and increases in the number of real-time ionospheric measurements, forecasting ionospheric conditions with systems similar to the one described here will become routine in the very near future. This article aims to give a reader from the GPS community a high-level overview of system principles, design, and operations as well as outline current data delivery mechanisms. Additionally, we describe planned extensions of the model to scintillation forecasting and the impact of intense solar activities. Web-based access to the system is provided to early users for validation and exploration purposes at http://www.gpscorrections.com
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	408 - 419
Cite this article:	Khattatov, B., Murphy, M., Gnedin, M., Cruickshank, B., Boisvert, J., Sheffel, J., Jayaraman, V., Fuller-Rowell, T., "An Ionospheric Forecasting System," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 408-419.
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