Dynamics of Cometary Environments

AST 0707283 Combi关于彗星作为一个群体的组成和结构的大多数信息仍然来自对彗星或大气中气体和尘埃观测的模型分析。对包括彗星在内的所有行星大气层的研究已经达到了需要进行复杂的模型模拟以理解和解释其全球分布和动态的阶段。这个彗星建模程序独特地解决了彗星彗发现象和物理制度的国家的最先进的数值模拟代码的全方位。Combi和Gombosi博士在将这些代码直接应用于观察分析方面具有丰富的经验。模型的持续发展得益于计算机能力（速度、处理器和内存数量）的快速扩展以及能够应用多维模拟技术的高性能算法。 这种紧密结合的方法对于研究多尺度现象是独特的，特别强大，从表面附近的米到距离原子核数千万公里的尺度。在彗星中，各种物理和化学过程在高度不同的尺度上运行，因此这种方法对于理解广泛的空气动力学、尘埃气体动力学和等离子体物理过程之间的微妙相互作用具有特别重要的意义。该项目的长期目标是开发和应用多尺度、自洽的彗星大气中性粒子和等离子体综合建模能力，从复杂的3D核心延伸到数千万公里外的原子彗发和尾部以及受污染的（彗星拾取离子）太阳风。该模型将支持分析和解释彗星发展各个阶段的彗星环境的光谱和形态观测。本资助期内的具体科学目标代表了拟议研究的知识价值，具体科学目标如下：1.结合联合收割机三维尘埃气体动力学和三维磁流体动力学（MHD）模型与核表面/彗发边界层的热物理模型描述，为理解整个观测范围的彗星彗发现象提供一个独特的建模工具.将多组分（多连续性方程）MHD应用于彗星，并对太阳风的时变效应（IMF方向、等离子体片交叉等）进行完整的参数研究。对离子尾的影响，以及利用稳态模拟对彗星等离子体环境随气体产生率、日心距和太阳风条件的总体全球变化进行参数研究.首次对彗星进行了电阻霍尔MHD计算。以我们的三维MHD模型为基础，大大扩展和推广计算彗星详细X射线辐射的综合能力。使用不断发展的新建模工具来解释各种过去彗星以及机会目标彗星的观测结果，包括离子和X射线观测结果。最后，该项目在其教育部分具有广泛的影响，将为培训一名研究生提供支持，此外，模型中物理和数值方法的继续发展将有利于基本代码的其他应用。从一种应用到另一种应用，对数字代码的所有应用都有很大的好处。

AST 0707283CombiMost information about the composition and structure of comets as a group continues to come frommodel analyses of observations of gas and dust in their comae, or atmospheres. The study of all planetary atmospheres, including comets, has reached the stage where complex model simulations are required to understand and interpret their global distribution and dynamics. This comet-modeling program uniquely addresses the full range of cometary coma phenomena and physical regimes with state-of-the-art numerical simulation codes. Drs. Combi and Gombosi have the demonstrated experience in applying these codes directly to the analysis of observations. Continuing development of models benefits from the rapid expansion in capabilities of computers (speed, number of processors and memory) and high performance algorithms enabling multi-dimensional simulation techniques to be applied. The tightly integrated approach of this effort is unique and particularly powerful for the study of multiscale phenomena, from the scale of meters near the surface to tens of millions of km far from the nucleus. In comets various physical and chemical processes operate on highly disparate scales, therefore this methodology has particular significance for understanding the delicate interplay between a wide range of aeronomical, dusty gas dynamic and plasma-physical processes. The long term goal of this project is the development and application of a multiscale, self-consistentcomprehensive modeling capability for neutrals and plasma in cometary atmospheres extending from the complex 3D nucleus to tens of millions of kilometers into the outer atomic coma and tail and the contaminated (by cometary pick-up ions) solar wind. The model will support analysis and interpretation of spectroscopic and morphological observations of cometary environments at all stages of its development. Specific scientific objectives for this funding period, which represent the intellectual merit, of theproposed research are:1. To combine 3D dusty-gas kinetics and 3D magnetohydro-dynamic (MHD) models with a thermo-physical model description for the nucleus surface/coma boundary layer to make a unique modeling tool for understanding the entire range of observed cometary coma phenomena.2. To apply multispecies (multiple continuity equations) MHD to comets and to perform a complete parameter study of the effects of time-variations of solar wind (IMF direction, plasma sheet crossings, etc.) on the ion tail, as well as using steady-state simulations for a parameter study of the overall global variation of the comet plasma environment with gas production rate, heliocentric distance and solar wind conditions.3. To perform the first resistive Hall MHD calculations for comets.4. To considerably expand and generalize the integrated capability to calculate detailed x-ray emissions in comets using our 3D MHD model as a basis.5. To use the evolving new modeling tools for interpreting observations from a variety past comets as well as target-of-opportunity comets including ion and x-ray observations.Finally, the project has a significant broader impact in its educational component that will provide support in the training one graduate student, and additionally that the continued development of the physical and numerical methods in the models will benefit to other applications of the basic codes.This cross talk from one application to another has an established history of great benefit to allapplications of the numerical codes.***