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首页> 外文期刊>Astronomy and astrophysics >The near-nucleus gas coma of comet 67P/Churyumov-Gerasimenko prior to the descent of the surface lander PHILAE
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The near-nucleus gas coma of comet 67P/Churyumov-Gerasimenko prior to the descent of the surface lander PHILAE

机译：表面着陆器PHILAE下降之前67P / Churyumov-Gerasimenko彗星的近核气昏迷。

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Context. The European Space Agency (ESA) Rosetta mission was the most comprehensive study of a comet ever performed. In particular, the Rosetta orbiter, which carried many instruments for monitoring the evolution of the dusty gas emitted by the cometary nucleus, returned an enormous volume of observational data collected from the close vicinity of the nucleus of comet 67P/Churyumov-Gerasimenko. Aims. Such data are expected to yield unique information on the physical processes of gas and dust emission, using current physical model fits to the data. We present such a model (the RZC model) and our procedure of adjustment of this model to the data. Methods. The RZC model consists of two components: (1) a numerical three-dimensional time-dependent code solving the Eulerian/Navier-Stokes equations governing the gas outflow, and a direct simulation Monte Carlo (DSMC) gaskinetic code with the same objective; and (2) an iterative procedure to adjust the assumed model parameters to best-fit the observational data at all times. Results. We demonstrate that our model is able to reproduce the overall features of the local neutral number density and composition measurements of Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) Comet Pressure Sensor (COPS) and Double Focusing Mass Spectrometer (DFMS) instruments in the period August 1–November 30, 2014. The results of numerical simulations show that illumination conditions on the nucleus are the main driver for the gas activity of the comet. We present the distribution of surface inhomogeneity best-fitted to the ROSINA COPS and DFMS in situ measurements.
机译：上下文。欧洲航天局（ESA）的罗塞塔任务是对彗星进行的最全面的研究。尤其是，罗塞塔（Rosetta）轨道器搭载了许多监测彗星核发射的粉尘气体演变的仪器，返回了从彗星67P / Churyumov-Gerasimenko核附近附近收集的大量观测数据。目的使用当前适合数据的物理模型，此类数据有望产生有关气体和粉尘排放物理过程的独特信息。我们提出了这样一个模型（RZC模型）以及该模型针对数据的调整过程。方法。 RZC模型包括两个部分：（1）求解控制气体流出的欧拉/ Navier-Stokes方程的数字三维时间相关代码，以及具有相同目标的直接模拟蒙特卡洛（DSMC）气体动力学代码; （2）迭代程序来调整假设的模型参数，以始终最佳地拟合观测数据。结果。我们证明了我们的模型能够再现用于离子和中性分析（ROSINA）彗星压力传感器（COPS）和双聚焦质谱仪（DFMS）仪器的Rosetta轨道仪的局部中性数密度和成分测量的总体特征数值模拟的结果表明，原子核上的光照条件是彗星气体活动的主要驱动力，时间为2014年8月1日至11月30日。我们介绍了最适合ROSINA COPS和DFMS原位测量的表面不均匀性分布。

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