The density and temperature structure near the exobase of Saturn from Cassini UVIS solar occultations
The density and temperature structure near the exobase of Saturn from Cassini UVIS solar occultations
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卡西尼号 UVIS 太阳掩星显示土星外底附近的密度和温度结构
DOI：
10.1016/j.icarus.2013.07.037
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发表时间：
2013
期刊：
影响因子：
3.2
通讯作者：
S. Edgington
中科院分区：
文献类型：
--
作者：
T. Koskinen;B. Sandel;R. Yelle;F. Capalbo;G. Holsclaw;W. McClintock;S. Edgington
我们分析了卡西尼UVIS仪器观测到的15个太阳掩星，以限制土星外底附近的密度和温度结构。我们通过分析波长小于804 nm的H2电离连续谱反演了H2的密度，从而反演了1 bar水平以上1900 km高度处的温度。我们发现，外逸层温度范围为370 - 540 K，典型的不确定度小于20 K。根据我们的数据，温度从赤道到两极随纬度增加100-150 K。在相似的纬度，温度在不同的时间变化20-50 K，到目前为止没有任何系统的昼夜趋势的证据。根据我们的数据，土星的外底是2700-3000公里以上的1巴水平和外底附近的热逸参数范围从260到340，这意味着从土星的热逸是坚定的金斯制度。H2的混合比在所有海拔高度以下的外底接近统一。我们发现，在热层的压力水平显着偏离一个简单的球体预测的潜在的理论。这与低热层中显著的纬向温度变化是一致的。需要对大气层不同深度的温度结构进行全球分析，以进一步限制高层大气的形状以及能量的沉积和再分布。
We analyzed 15 solar occultations observed by the Cassini UVIS instrument to constrain the density and temperature structure near the exobase of Saturn. We retrieved the density of H2and thus the temperature at altitudes higher than 1900 km above the 1 bar level by analyzing the ionization continuum of H2at wavelengths shorter than 804 Å. We find that the exospheric temperature ranges from 370 K to 540 K, with a typical uncertainty of less than 20 K. According to our data the temperature increases with latitude from the equator to the poles by 100–150 K. At similar latitudes, the temperature varies by 20–50 K at different times with no evidence for any systematic diurnal trend so far. Based on our data, the exobase of Saturn is 2700–3000 km above the 1 bar level and the thermal escape parameter near the exobase ranges from 260 to 340, implying that thermal escape from Saturn is firmly in the Jeans regime. The mixing ratio of H2is close to unity at all altitudes below the exobase. We find that the pressure levels in the thermosphere deviate significantly from a simple spheroid predicted by potential theory. This is consistent with significant meridional temperature variations in the lower thermosphere. A global analysis of the temperature structure at different depths in the atmosphere is required to constrain both the shape and the deposition and redistribution of energy in the upper atmosphere further.
太阳周期24：太阳在做什么？
影响因子：
0.8
作者：
Lockwood M
通讯作者：
Lockwood M