Science Issues And Challenges

There are a number of challenges facing ionospheric specialists and aeronomists. While theories explaining most facets of ionospheric behavior exist and are generally accepted, the theories do not always provide a good basis for prediction of future behavior. This is because the driving forces and boundary conditions needed in a physical model are not always known, and estimates must be used. This has led to the development of semi-empirical models for the purpose of system design and these are used for operations as well. By and large these models exploit large ionospheric data bases and yield only median representations of ionospheric parameters. To fix this problem, various "update" schemes have been developed to make the specification of the ionospheric state as current as possible. The physics is then used to let the system evolve. The new GAIM methodologies offer some considerable promise in this regard. Still, all of this can be very unsatisfactory unless an understanding of the nature of ionospheric variability (viz., in both space and time) is established. There are many sources within the earth-sun system that contribute to the growth of ionospheric structure. While these have been characterized to some extent, the characterizations are not sufficient to provide predictions acceptable for many users of the ionospheric channel. Currently this is a major challenge facing the ionospheric research community. Even GAIM technology will be taxed in its quest to map medium-to-small scale ionospheric structure and disturbances, including TIDs.

The following topics require more attention from ionospheric specialists: (a) the driving forces of upper atmospheric winds and the impact on ionospheric structure and dynamics; (b) the hierarchy of energy sources within the earth-sun system that influence ionospheric behavior; (c) the development of geomagnetic storms and the impact that storms have on ionospheric behavior; (d) the development and evolution of ionospheric inhomogeneities; and (e) various methods for ionospheric predictions.

Finally, in the new millennium, the researcher is confronted with an enormous amount of data, both near real-time and archived, that may be accessed via the Internet. Harnessing this information stream, and using the state-of-the-art computational assets, it should be possible to leverage ongoing science efforts, organize more efficient experimental campaigns, and enhance collaborative efforts, all resulting in a more fulsome understanding of ionospheric physics.

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