Studies on production processes of exospheric atmospheres of Mercury and Io based on development of a spectro-imager

1. 研制了一种用于探测行星和卫星外大气层钠辐射的光谱成像系统。该系统包括：1)由光纤束构成的尺寸转换光学器件；2)将尺寸转换光学器件连接到光入口和光出口的f数调节光学器件。光纤束按12x12（入口）和144x1（出口）排列。该系统安装在光学台上，与东北大学直径60cm的coude望远镜（入口侧）和高分辨率光栅光谱仪（出口侧）相连。光谱基准被投射到Li-N2冷却CCD相机上，并在计算机上重建成光谱图像。用光谱成像系统对伽利略卫星之一的木卫一和水星的外逸层大气进行了观测。有人认为，更多的木卫一大气的产生速率取决于木卫一的相位角（木卫一相对于木星的明显位置）。为了证实这种相关性，我们对木卫一进行了不同相位角的观测，获得了重要的数据集。另一方面，人们对水星进行了大量的观测，因为水星在很大程度上是在远离太阳的情况下观测的。由于主要地区恶劣的天气条件，研究期间没有获得足够的可靠的产气过程图像。我们计划在2006年6月之后进行后续观测，届时水星将在2006年远离太阳的情况下被观测到。建立了蒙特卡罗模拟模型，并采用该模型对采气过程进行了数值模拟。水星大气层的结果表明，太阳风质子的离子溅射比之前预测的更有效地在水星表面产生了大气层。对于木卫一的大气，我们推测大气的数量可能是由木星磁层等离子体溅射和/或对等与太阳光激发光子解吸的耦合过程控制的。少

1. Development of a 2D spectro-imaging system for exospheric atmospheresA spectro-imaging system for detection of sodium emissions of exospheric atmospheres of planets and satellites is developed. The system consists of 1)a dimension converting optics made of an optical fiber bundle, and 2)a F-number adjusting optics to connect the dimension converting optics to light-entrance and exit optics. The optical fiber bundle is arranged in 12x12(entrance) and 144x1(exit). The system is set up on an optical bench and connected to the 60cm diameter coude telescope (entrance side) and high-resolution grating spectrometer (exit side) of Tohoku University. A spectrum datum is projected onto a Li-N2 cooled CCD camera and reconstructed to a spectro-image on a computer.2. Observations of exospheric atmospheres of Io and MercuryObservations of exospheric atmospheres of Io, one of the Galilean satellites, and Mercury have been made using the spectro-imaging system. It has been suggested that production … More rate of Io's atmosphere depends on Io's phase angel (Io's apparent position with respect to Jupiter). In order to confirm the dependence, we have made observations of Io for various Io's phase angles and obtained significant data-sets. On the other hand, Mercury observations have been made intensively for the period when Mercury is viewed largely apart from the sun. Due to bad weather condition in main, reliable images for investigating gas production processes have not been sufficiently acquired in the research period. We plan to make follow-up observations after June, 2006 when Mercury is viewed most largely apart from the sun in 2006.3. Numerical simulation for investigating gas production processesA Monte-Carlo simulation model has been developed and adopted for the investigations of gas production processes. As the result for Mercury's atmosphere, it is suggested that ion sputtering by solar wind protons is operated further more effectively than previously predicted on Mercury's surface to product the atmosphere. As for Io's atmosphere, it is inferred that the amount of the atmosphere might be controlled by the coupling process of sputtering and/or peering by Jupiter's magnetospheric plasma and the photon stimulated desorption by the sunlight. Less