Electron Precipitation Models in Global Geospace Simulations

The ability to forecast the weather of the geospace environment depends critically on the ability to accurately model the dynamics of the coupled magnetosphere-ionosphere (MI) system. The MI interaction involves a set of electrodynamic and plasma transport processes acting between the magnetosphere and ionosphere, and it is influenced by precipitating particles that deposit both thermal and kinetic energy from the magnetosphere in the ionosphere. Satellite data show that there are four principle types of auroral electron precipitation: monoenergetic, diffuse, broadband and secondary electron precipitation.;Global simulations play an important role in understanding the coupled MI system. A key feature of most global models is the implementation of magnetosphere-ionosphere (MI) coupling, and electron precipitation is one of the most important processes to specify. However, one deficiency of most global simulation codes is the lack of accurate specifications of electron precipitation. Preliminary results by the author using the Lyon-Fedder-Mobarr (LFM) global simulation model show that an improved model for electron precipitation can have significant effects on the characteristics of the MI system. This finding suggests that a sophisticated electron precipitation model is important to the fidelity of geospace environmental modeling.;The principle objectives of the thesis are to improve the existing diffuse and monoenergetic electron precipitation model and to implement broadband and cusp electron precipitation models in the LFM code. The diffuse electron precipitation model is improved by introducing a dynamically regulated boundary, and the monoenergetic electron precipitation model is improved by using anomalous resistivity current-voltage relation. Broadband electron precipitation is regulated by the downward AC Poynting flux, together with empirical relations derived from satellite data. Cusp electrons are specified based on the cusp identification algorithm used in the global simulation.;The improved electron precipitation models are used to study the effect of precipitating electrons on the electrodynamics of MI interaction in LFM. The new electron precipitation models improve the accuracy and forecasting ability of global simulation models demonstrated by comparison with both empirical model and observations. Also, soft (< 500 eV) electron precipitation modifies the state of F-region ionosphere and thermosphere significantly when LFM is coupled to a thermosphere-ionosphere general circulation model.