Monte Carlo modeling of exospheric bodies - Mercury
Monte Carlo modeling of exospheric bodies - Mercury
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外层天体的蒙特卡罗建模 - 水星
DOI：
10.1029/ja083ia08p03783
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发表时间：
1978
影响因子：
--
通讯作者：
L. Wallace
中科院分区：
文献类型：
--
作者：
Gerald R. Smith;D. Shemansky;A. Broadfoot;L. Wallace
先前对水星和月球氦外逸层的模型计算基于这样一种情况，其中每个氦原子与表面的撞击都会导致从给定源分布中选择一个新粒子。选择源粒子中的特定速度空间分布的隐含意图是，所产生的大气在理想条件下将是气压的。实际上，已发布的计算中使用了两种粒子源分布，我们在此将其描述为麦克斯韦-玻尔兹曼 (M-B) 和麦克斯韦-玻尔兹曼通量 (M-B-F)。在计算了地表以上区域的大气分布的情况下，所得的模型大气代表了 M-B 和 M-B-F 源的混合。我们认为，已发表的两个天体的外大气层计算均不能代表气压粒子源产生的大气。尽管从表面物理学的角度来看，气压粒子源是不合理的，但由这种源产生的外逸层对于基于更现实的条件的计算来说是一个有价值的参考点。根据下面的分析，如果将分布中的颗粒视为通量的组成部分，则适当的源分布应为 M-B-F。使用 M-B-F 源进行的蒙特卡罗计算与 Mariner 10 紫外光谱仪数据进行了比较。比较表明现有模型无法拟合观测到的水星外逸层。
Previous model calculations of the helium exospheres of Mercury and the moon have been based on a regime in which each helium atom impact with the surface results in the selection of a new particle chosen from a given source distribution. The particular velocity space distribution in the source particles was chosen with the implied intent that the resulting atmosphere would be barometric under ideal conditions. In effect, two particle source distributions have been used in the published calculations, which we describe here as Maxwell-Boltzmann (M-B), and Maxwell-Boltzmann flux (M-B-F). In the instances in which the atmospheric distribution has been calculated for regions above the surface, the resulting model atmosphere represents a mixture of the M-B and M-B-F sources. We suggest that none of the published exospheric calculations for the two bodies represent atmospheres produced by a barometric source of particles. Although a barometric source of particles cannot be justified in terms of surface physics, an exosphere produced by such a source is a valuable point of reference for calculations based on more realistic conditions. According to the analysis presented below, the appropriate source distribution should be M-B-F if the particles in the distribution are to be treated as components of flux. Monte Carlo calculations with an M-B-F source are compared with Mariner 10 ultraviolet spectrometer data. The comparison suggests that present models are incapable of fitting the observed Mercury exosphere.