Studies of release and loss processes of Mercury's atmosphere investigated with ground based optical observations

1)水星大气二维成像系统的研制成功了基于日冕照相技术的水星大气弱发射层二维成像探测系统。观测波长设置在Na-D线的发射处。明亮发射区（观测对象）周围的弱发射与明亮区之间的对比度达到1：1000。2）水星大气的观测：现状2001年12月和2002年4月进行了观测。由于季节性的风和水星的低海拔造成的硬大气涂抹效应，这些时期的可靠图像尚未成功获取。然而，我们可以建立观测和分析方法，这是需要得到的水星大气的弱发射层的二维图像。3）蒙特-卡罗模拟分析水星的大气的中性和电离粒子的蒙特-卡罗模拟分析已经进行了研究的水星的扩展大气，这是观察到的弱发射层的生成过程。结果表明，扩展大气的可能过程是离子溅射或/和陨石蒸发，弱发射层的定量二维成像对于确定适当的气体释放过程是非常重要的。

1) Development of the 2D imaging system for Mercury's atmosphericThe 2D imaging system for detection of the atmospheric weak emission layer surrounding Mercury is successfully developed based on the corona-graph technique. The observation wave length is set at the emissions of Na-D lines. The contrast between a weak emission surrounding a bright emission region (observation object) and the bright region is achieved to be 1:1000.2) Observations of Mercury's atmosphere: current statusThe observations were made for Dec. 2001 and April 2002. Due to a hard atmospheric smearing effect caused by a seasonal wind and low altitude of Mercury, reliable images have not been acquired successfully for the periods. However, we could establish observation and analysis methods which are required to derive 2D image of the weak emission layer of Mercury's atmosphere.3) Monte-Carlo simulation analysis for Mercury's atmosphereA Monte-Carlo simulation analysis for neutral and ionized particles has been made to investigate generation processes of Mercury's extended atmosphere, which is observed as the weak emission layer. As the result, it is suggested that plausible processes of the extended atmosphere are ion-sputtering or/and meteoritic vaporization, and the quantitative 2D imaging for the weak emission layer is quite important to determine the proper gas release process.