| 摘要: | 行星外氣層的結構與演化受到許多因素所影響，包含地表的產生率、與表土的交互作用、太陽風離子的濺射作用等等。為了更了解外氣層的本質，地表的特性和太陽風的交互作用都是很重要的相關議題。反之，我們也可以藉由從外氣層所導出的訊息，得知地表的特質、太陽風離子的撞擊形式和重離子的分佈。為此，雖然我們一開始分別討論各個主題，但最終的目標是想從整體上來認識在太陽系裡沒有大氣層的物體上，其元素之固態、氣態與電漿態的三種不同面向 。 本論文的課題是利用地表熱能模型、二維和三維外氣層模型和三維混合粒子電漿模型來學習水星外氣層與磁層的結構。在沒有豐厚的電離層影響的情況下，透過與觀測與測量的結果比較， 我們學習到外氣層的特徵與其地表的交互作用，還有包括了基本的磁層形態。當結合地表熱能模型所導出的溫度分佈與外氣層模型之後，我們計算出水星外氣層氣體的熱平衡狀態，其中包含了生命期較長的氦與氧原子氣體，和生命期較短的鈉原子氣體。我們也應用混合粒子模型來了解信使號太空船兩次飛過水星時所量測到的表面離子滲透分佈與磁層結構。將來如果結合外氣層與混合粒子兩種模型的結果，從外氣層氣體游離出來之重離子的流動狀態也會是個值得加以討論的議題。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. |
