Practical SPH models for major planets
Practical SPH models for major planets
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主要行星的实用 SPH 模型
DOI：
10.1111/j.1365-2966.2007.11498.x
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发表时间：
2007
影响因子：
4.8
通讯作者：
M. Woolfson
中科院分区：
文献类型：
--
作者：
M. Woolfson
建立行星模型有两个主要原因：第一是为了进一步了解它们的内部结构，第二是为了提供模型来探索行星发挥作用的天体物理情况。由于后一个原因，对精度的要求不那么严格，尽管行星的主要特征必须是现实的。一个层状巨行星的数值模型是由一个铁核，一个硅酸盐地幔，一个冰区和一个氢氦大气层开发的。使用Tillotson状态方程，并给出两个模型行星的例子，一个复制木星的质量和半径相当接近，另一个有两个木星的质量。将这些结果转移到光滑粒子流体动力学（SPH）模型中存在两个主要困难。SPH点的均匀分布导致表示非大气分量的点太少。它表明，使用扭曲的晶格，使核心+硅酸盐+冰被代表的几百个点，使这些地区的演变可以详细跟踪。另一个困难是层状结构中密度的不连续性。SPH点的密度估计值在材料界面附近要么太大要么太小，导致不切实际的压力梯度，从而导致大的和非物理的局部力。算法描述，以避免这种困难，在物质界面和附近的表面的星球。在一些天体物理学的情况下，涉及SPH模型的行星，行星的主要部分是如此不透明，内部热传递可以忽略不计。然而，表面区域应该辐射，并且描述了包括来自行星表面的辐射的方便方式。
Modelling planets is done for two main reasons ‐ the first to further understanding of their internal structure and the second to provide models to explore astrophysical situations in which planets play a role. For the latter reason, the requirements on accuracy are less severe, although the planet must be realistic in its major features. A numerical model of a layered giant planet is developed with an iron core, a silicate mantle, an ice region and a hydrogen‐ helium atmosphere. The Tillotson equation of state is used and examples of two model planets are given, one reproducing the mass and radius of Jupiter quite closely and the other with two Jupiter masses. Transferring these results into a smoothed particle hydrodynamics (SPH) model presents two main difficulties. A uniform distribution of SPH points leads to too few points representing the non-atmospheric component. It is shown that using a distorted lattice enables the core + silicate + ice to be represented by several hundred points so that the evolution of these regions can be followed in detail. Another difficulty concerns the density discontinuities attendant on a layered structure. Density estimates of SPH points are either too large or too small near material interfaces leading to unrealistic pressure gradients and, consequently, to large and unphysical local forces. Algorithms are described for avoiding this difficulty both at material interfaces and near the surface of the planet. In some astrophysical situations involving SPH-modelled planets, the main bulk of the planet is so opaque that internal heat transfer can be neglected. However, surface regions should radiate and a convenient way for including radiation from a planetary surface is described.