Scattering particles in nightside limb observations of Venus’ upper atmosphere by Venus Express VIRTIS
Scattering particles in nightside limb observations of Venus’ upper atmosphere by Venus Express VIRTIS
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金星快车 VIRTIS 对金星高层大气夜侧边缘观测中的散射粒子
DOI：
10.1016/j.icarus.2010.08.023
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发表时间：
2011
期刊：
影响因子：
3.2
通讯作者：
P. Drossart
中科院分区：
文献类型：
--
作者：
R. Kok;P. Irwin;C. Tsang;G. Piccioni;P. Drossart
由金星快车VIRTIS获取的金星高层大气的夜间红外边缘光谱显示出热辐射的强烈散射。这种向上辐射向视线的散射在82.5公里以下占主导地位，即使在波长为5μm的情况下也是如此，这表明粒子相对较大。我们发现，1μm大小的硫酸粒子(也称为模式2粒子)与高海拔地区的VIRTIS肢体数据非常吻合。在20-30°N和47-50°N两个纬度范围内，我们反演了75-90公里范围内模2数密度的垂直剖面。在20-30°N范围内，模2粒子的散射是80-85公里高度辐射的主要来源。高度在85公里以上的较小粒子也可以用来拟合光谱。在47°N和50°N之间，模2的数密度一般低于20°N和30°N之间的数密度，并且剖面表现出更大的变异性。这与位于低纬度和高纬度之间的47-50°纬度区域是一致的，后者显示出较低的云顶和较高的紫外线亮度(Tiov，D.V.，Taylor，F.W.，Svedem，H.，Ignatiev，NI.，Markiewicz，W.J.，Piccioni，G.，Drossart，P.[2008]。自然456,620-623)。
Nightside infrared limb spectra of the Venus upper atmosphere, obtained by Venus Express VIRTIS, show strong scattering of thermal radiation. This scattering of upward-going radiation into the line-of-sight is dominant below 82.5km even at a wavelength of 5μm, which is indicative of relatively large particles. We show that 1μm-sized sulfuric acid particles (also known as mode 2 particles) provide a good fit to the VIRTIS limb data at high altitudes. We retrieve vertical profiles of the mode 2 number density between 75 and 90km at two latitude ranges: 20–30°N and 47–50°N. Between 20 and 30°N, scattering by mode 2 particles is the main source of radiance for altitudes between 80 and 85km. Above altitudes of 85km smaller particles can also be used to fit the spectra. Between 47 and 50°N mode 2 number densities are generally lower than between 20 and 30°N and the profiles show more variability. This is consistent with the 47–50° latitude region being at the boundary between the low latitudes and high latitudes, with the latter showing lower cloud tops and higher ultraviolet brightness (Titov, D.V., Taylor, F.W., Svedhem, H., Ignatiev, N.I., Markiewicz, W.J., Piccioni, G., Drossart, P. [2008]. Nature 456, 620–623).