Plasma environment around comet 67P

与以往几小时内飞越彗星的彗星任务不同，欧洲航天局的罗塞塔任务护送彗星67P的旅程长达两年，从距离太阳3.6天文单位的距离到1.2天文单位的近日点，再到任务结束时3.8天文单位的距离。结果，它收获了丰富的、前所未有的中性和等离子体环境数据集，涵盖了大范围的日心距离、季节、纬度、经度、放气和太阳活动。论文的目的是探索彗星周围的等离子体环境在护航阶段是如何演变的，并将其与遥感观测联系起来。离子和中性质谱仪的测量结果将被利用，利用仪器提供的高质量分辨率。将评估不同相互作用区域中离子组成随时间的演变。研究结果将与模拟结果进行比较，以推断化学与输运的相对重要性，并解决一个非常令人困惑的离子动力学问题。碰撞与传输的作用也将被评估为极光发射，包括在高排气活动时亮度下降的红线。

Unlike previous cometary missions which flew by a comet in a few hours, the European Space Agency Rosetta mission escorted comet 67P over a two-year journey, from a distance distance of 3.6 au from the Sun to perihelion at 1.2 au and to the end of mission at 3.8 au. As a result, it harvested a rich and unprecedented dataset of the neutral and plasma environment over a large range of heliocentric distance, season, latitude, longitude, outgassing and solar activity. The aim of the thesis will be to explore how the plasma environment around the comet evolved over the escort phase and to link it to remote-sensing observations. Measurements from the ion and neutral mass spectrometer will be exploited, taking advantage of the high mass resolution offered by the instrument. The evolution of ion composition over time in different interaction regions will be assessed. The findings will be compared with modelled outputs in order to infer the relative importance of chemistry versus transport and address a very puzzling question on ion dynamics. The role of collisions versus transport will also be assessed for auroral emissions, including the red line whose brightness decreases at high outgassing activity.