Model-based optical and radar remote sensing of transport and composition in the auroral ionosphere

The terrestrial ionosphere is heavily influenced by electrodynamic and inertial coupling with the magnetosphere. This coupling is most apparent at high latitudes where precipitating electrons and electromagnetic disturbances associated with auroras greatly alter temperatures and motions of the ionospheric plasma. Among other effects, auroral electrons are responsible for heating ionospheric electrons and producing ion upflows. Perpendicular electric fields frictionally heat ionospheric ions, resulting in drastic modifications to chemical reaction rates which control F-region ion composition. The lasting effects of upflows and composition on the magnetosphere-ionosphere system are poorly understood due to a sparsity of measurements of these processes. This shortage of measurements is addressed by developing two new remote sensing techniques: one for estimating ion upflows from optical measurements and another for estimating ion composition from incoherent scatter radar (ISR) data.;This research develops an underutilized diagnostic for ion upflows: auroral optical emissions. Systematic theoretical modeling efforts demonstrate that emission features with wavelengths of 630.0 nm, 732-733 nm, and 844.6 nm are ideal indicators of upflow. A technique is then developed which uses multi-spectral auroral optical measurements to estimate ion upflow. This technique is applied in two steps: (1) multi-spectral optical data are inverted, using a physics-based kinetic model of electron energy deposition, to estimate electron precipitation; (2) this precipitation is used as input to a ionospheric model to calculate the resulting ion upflow. This technique is applied to near-infrared (700-850 nm wavelength) optical observations from an event occurring on 17 February 2001 at the Sondrestrom research facility. Estimated ion upflow is shown to be accurate through quantitative comparisons with concurrent ISR observations.;A method for estimating ion composition from ISR data is also developed in this research. The ion mass-temperature ambiguity is addressed by using a physics-based model of ion frictional heating to specify ion temperature, and then interpreting the ISR measurements in terms of the ion composition which best explains the observed profiles. The ion composition estimator is applied to measurements recorded by the Sondrestrom ISR taken on 26 February 2001, a time when the F-region ionosphere is severely disturbed by a nearby auroral arc. The molecular to atomic ion transition altitude varies during the 20 minute event from ∼205 to 325 km, and is observed to change by as much as 100 km over a one minute period. These estimates are corroborated by fluid model simulations and demonstrate the highly variable nature of auroral ion composition and problems it poses for standard ISR analysis methods.;Both of the estimation techniques developed in this work use physics-based models to effectively extend the observable domain of the sensors with which they are applied. These methods allow for inferences not possible using their component models or data separately. The optical estimation technique provides a means for better coverage of auroral zone upflows since optical sensors are inexpensive and may be deployed in large networks. The ion composition estimator addresses a source of systematic error in ISR observations and provides a means to observe the poorly-understood behavior of high-latitude composition.