VALIDATION OF TECHNIQUES FOR SPACE-BASED REMOTE-SENSING OF AURORAL PRECIPITATION AND ITS IONOSPHERIC EFFECTS

Knowledge of the spatial distribution of auroral precipitation and its associated ionospheric effects is important both to scientific studie s of the Earth's environment and successful operation of defense and c ommunication systems. Observations with the best spatial and temporal coverage are obtained through remote sensing from space-based platform s. Various techniques have been used, including the detection of visib le, ultraviolet and X-ray emissions produced by the precipitating part icles. Interpretation of the measurements is enabled through theoretic al modeling of the interaction of precipitating particles with atmosph eric constituents. A great variety of auroral precipitation exists, wi th each kind differing in the type and energy distribution of the part icles, as well as in its spatial and temporal behavior. Viable remote sensing techniques must be able to distinguish at least the species of particle, the total energy flux, and the average energy. Methods base d on visible, ultraviolet and X-ray emissions meet these requirements to varying degrees. These techniques and the associated space instrume ntation have evolved in parallel over the last two decades. Each of th e methods has been tested using simultaneous measurements made by spac e-based imaging systems and groundbased measurements made by radars an d optical instruments. These experiments have been extremely helpful i n evaluating the performance and practicality of the instruments and t he results have been crucial in improving instrument design for future remote sensing platforms. The next decade will see continued developm ent and test of remote sensing instruments and the measurements, in ad dition to providing important operational data, will be increasingly m ore critical in addressing a number of scientific problems in auroral and atmospheric physics.