演講資訊

摘要：

Europa has been suggested to have a subsurface ocean from a diversity of surface geological features and the magnetic field and plasma measurements made by the Voyagers and Galileo missions (i.e., Anderson et al., 1998; Kivelson et al., 2000; Greenberg, 2005). In addition, Europa is also spotted to have the water outgassing activities, similar to those plumes of Enceladus associated with its subsurface ocean, by the space and ground telescopes as well as reinvestigating the Galileo data (Roth et al., 2014; Sparks et al., 2016, 2017; Paganini et al., 2020; Jia et al., 2018; Arnold et al., 2019; Huybrighs et al., 2020). In this work, we use a 3D Direct Simulation Monte Carlo (DSMC) model to study the plume structures of Europa (i.e., Lai et al., 2019). This model can describe the gas plumes with a broad flow regime ranging from close to continuum near the surface to free-molecular condition at higher altitudes. With a systematic study of a large parametric space of the total gas production rate and initial gas ejection velocity, the gas number density, temperature and velocity information of outgassing activity at various scales can be derived. In addition, the modeling results will be incorporated with a n-LTE radiative transfer model to simulate the water plume morphology which could be observed in the sub-millimeter and millimeter wavelengths. Understanding the plume of Europa and its effects (i.e., icy dust deposit on surface) plays a key role to probe its interior structure and outgassing mechanism (i.e., cryovolcanism). Our results can be well prepared for the space and ground telescope observations (i.e., ALMA) and the in-situ measurements of the future spacecraft missions such as JUICE and Europa Clippers.