| Summary: | 碩士 === 國立中央大學 === 天文研究所 === 105 === Thanks to the Rosetta Mission, we have an opportunity to study comet 67P/C-G in the long journey from Aug. 2014 to the end of Sep. 2016. This is the first time to orbit and land on the comet.
According to Feldman et al. (2015) and Bodewits et al. (2016), some of the atomic and molecular emissions such as O1, H1, OH, etc. might be attributed to electron impact dissociation. As a result, we want to understand the effect of the electron impact mechanism on the cometary coma. An ion-neutral chemical model in used to estimate the number density ratio of H3O+/H2O+ under different physical conditions.
For the model setting, to account for the seasonal effect, we consider two heliocentric distances: 3 AU and 1.2 AU, i.e., the perihelion, respectively. The surface composition of the comet in further divided into two parts: the Northern and Southern hemisphere. We also use three different electron energy spectra (Maxwellian distribution/ source spectra due to the photoionization/ observation from Rosetta ) to simulate the resultant coma structure.
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