发表机构
Southwest Research Institute; Khan Enterprises LLC; Observatoire de Paris/PSL; Instituto de Astrofisica de Andalucia（西南研究所; 汗企业有限责任公司; 巴黎天文台/PSL; 安达卢西亚天体物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用TEXES光谱仪的191次观测，通过改进建模和时间归一化得到木卫一昼侧SO₂柱密度的近日点和远日点经度分布，发现其存在半球不对称性，日食效应重要但霜分布也有作用。
AI 中文摘要
自2001年以来，我们利用美国国家航空航天局红外望远镜设施的TEXES高分辨率中红外光谱仪研究木卫一（Io）以二氧化硫（SO₂）为主的大气密度。这些光谱覆盖了530 cm⁻¹附近的多条SO₂吸收线，用于反演赤道SO₂柱密度。除了覆盖较长的时间跨度外，我们的191次独立观测还覆盖了木卫一中心经度的全范围，使我们能够比以往更深入地研究木卫一昼侧大气的经度变化。通过改进对经度变化的建模，并利用季节模型对反演得到的SO₂密度进行时间归一化，我们得到了木卫一赤道SO₂柱丰度的两个完整经度分布，分别代表近日点和远日点。两者均呈现出以往研究中观测到的半球不对称性，最高密度出现在200°W附近，最低密度出现在305°W附近。我们发现，远日点时最大与最小密度的比值约为27，近日点时约为16。两个经度分布均不对称，木卫一 trailing 半球的密度下降比 leading 半球更陡峭。我们将这些经度分布与空间变化主要由火山活动、SO₂冰不均匀性或日食效应驱动时的预期分布进行了比较。我们得出结论，日食效应虽重要，但不足以解释观测到的经度变化形态，而霜分布可能也起着重要作用。
英文摘要
Since 2001, we have used the TEXES high resolution mid-infrared spectrograph at NASA's Infrared Telescope Facility to study the density of Io's SO$_{2}$-dominated atmosphere. The spectra cover several SO$_{2}$ absorption lines near 530 cm$^{-1}$ and are used to retrieve the equatorial SO$_{2}$ column density. In addition to covering a long time period, our 191 independent observations also cover the full range of Io central longitudes, allowing us to study the longitudinal variability of Io's dayside atmosphere in more depth than has previously been possible. By improving our modeling of longitudinal variability and using a seasonal model to apply a temporal normalization to the retrieved SO$_{2}$ densities, we produce two complete longitudinal distributions of Io's equatorial SO$_{2}$ column abundances, one representing perihelion and one representing aphelion. Both show the same hemispheric asymmetry that has been observed in previous studies, with the highest densities near 200W and the lowest densities near 305W. We find that the contrast between the maximum and minimum densities is a factor of ~27 at aphelion and a factor of ~16 at perihelion. Both longitudinal distributions are asymmetric, with a sharper drop-off on Io's trailing hemisphere than on the leading. We compare these longitudinal distributions to the distributions expected if the spatial variability were primarily driven by volcanic activity, SO$_{2}$-ice inhomogeneity or the effects of eclipses. We conclude that the effect of eclipses is important, but insufficient to explain the shape of the observed longitudinal variability, and frost distribution is likely to also be important.
CommentsAccepted for publication in The Planetary Science Journal (PSJ). 16 pages, 6 figures, and 1 table
