| Summary: | 博士 === 國立中央大學 === 天文研究所 === 100 === The structure and evolution of the exosphere on a planet involves numerous factors, including the source rate from the surface, the interaction with the regolith, the solar wind ion sputtering effect, and so on. In order to have a better understanding on the nature of the exosphere, the characteristics of the surface and the solar wind interactions are also important issues. Vice versa, the information hidden in the exosphere can give us clues on the surface properties, the solar wind ion bombardment patterns, and the heavy ion distributions. Therefore, although initially we have treated each topic separately, the ultimate objective is to apprehend the elements, with solid, gas, and plasma states, of a solar system object without an atmosphere as a whole.
In this work, the surface thermal model, 2D and 3D exospheric models, and the 3D hybrid model are applied to the studies on the exosphere and the magnetosphere structures of Mercury. Through the comparisons with the observations and measurements, we have learned the exospheric features and their interactions with the surface, as well as the fundamental morphology of the magnetosphere without the inclusion of a substantial ionosphere. The thermal accommodation effects on both longer lifetime exospheric atoms, helium and oxygen, and a shorter one, sodium, are calculated with our exospheric model combined with the surface temperature distribution from the thermal model on Mercury. The surface ion precipitation rate and the magnetosphere measured from the first two flybys of MESSENGER are also learned via the hybrid simulations. The circulations of the heavy ions produced from the exosphere is also an interesting subject to discuss with the joint results from the exospheric and the hybrid computations in future.
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