The cometary atmosphere and its interaction with the solar wind
The cometary atmosphere and its interaction with the solar wind
复制标题
彗星大气及其与太阳风的相互作用
DOI：
10.1029/rg020i004p00885
复制
发表时间：
1982
影响因子：
25.2
通讯作者：
H. Houpis
中科院分区：
文献类型：
--
作者：
D. Mendis;H. Houpis
我们对彗星大气及其与太阳风的相互作用的知识和理解的现状进行了批判性的回顾。在引言(第一节)之后，第二节回顾了彗星大气和彗尾的分光光度测定。第三节给出了关于大气丰度和各种分子物种的产生率的现有的相当零散的知识。讨论了从这些值可以推断出的原子核的化学成分及其不确定度。第四节对现有的包括电离层在内的彗星大气模型进行了批判性的评价。讨论了专注于化学而过分简化动力学的模型和专注于动力学和热力学而最小化化学的模型之间的持续二分法。强调了在未来将这两种方法结合起来的必要性。第五节讨论了彗星大气中的电离过程，强调除了与太阳风质子的光致电离和电荷交换电离外，在某些情况下，其他(碰撞)电离过程也可能对彗星中性物质的快速电离起作用。第6节讨论了太阳风-彗星相互作用的总体性质，特别强调了太阳风和彗星等离子体之间的强耦合，这是观测到的彗尾加速的原因。第七节讨论了彗星等离子体尾巴中观察到的复杂且随时间变化的精细结构。重点讨论了利用这些精细结构来推断等离子体尾巴中的磁场和相关电流的强度和形态，以及太阳风中的变化条件。第八节对彗星-太阳风相互作用的详细模型，从早期的流体动力学模型到最新的MHD模型进行了严格的评价，并强调了它们的局限性。它还指出，太阳风与彗星大气相互作用的性质是高度多变的，在某些情况下，外部和内部激波的性质都可能改变。此外，还强调有必要详细研究太阳风与新生的彗星大气在较大日心距离处的相互作用。综述以第9节结束，其中重点是彗星大气及其与太阳风的相互作用的突出问题。
The present state of both our knowledge and our understanding of cometary atmospheres and their interactions with the solar wind is critically reviewed. Following the introduction (section 1) the spectrophotometry of the cometary atmosphere and the tail is reviewed in section 2. The existing, rather fragmentary, knowledge about atmospheric abundances and the production rates of various molecular species is given in section 3. The deductions that can be made from these values about the chemical composition of the nucleus and their uncertainties are discussed. Existing models of the cometary atmosphere including the ionosphere are critically evaluated in section 4. The continuing dichotomy between models that concentrate on the chemistry while oversimplifying the dynamics and those that concentrate on the dynamics and thermodynamics while minimizing the chemistry is discussed. The need to combine these two approaches in the future is emphasized. The ionization processes in the cometary atmosphere are discussed in section 5. It is emphasized that besides photoionization and charge exchange ionization with the solar wind protons, other (collisional) ionization processes may play a role in the rapid ionization of cometary neutrals in certain situations. The overall nature of the solar wind-comet interaction is discussed in section 6 with special emphasis on the strong coupling between the solar wind and cometary plasmas, which is responsible for the observed accelerations in the cometary tails. The complex and time-varying fine structures observed in the plasma tails of comets are discussed next in section 7. The uses of these to infer the strength and morphology of the magnetic field and the associated currents in the plasma tail on one hand, and the varying conditions in the solar wind on the other, are emphasized. The detailed models of the comet-solar wind interaction, from the earlier fluid dynamic models to the latest MHD models are critically evaluated in section 8, and their limitations are underscored. It is also pointed out that the nature of the solar wind interaction with the cometary atmosphere is highly variable and that in certain circumstances the nature of both the outer and the inner shocks could change. Also, the need for a detailed study of the solar wind interaction with the fledgling cometary atmosphere at larger heliocentric distances is stressed. The review is concluded with section 9, where the emphasis is on the outstanding problems of cometary atmospheres and their interactions with the solar wind.