Future decreases in thermospheric density in very low Earth orbit

Future decreases in thermospheric density in very low Earth orbit
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未来极低地球轨道热层密度下降

DOI：
10.1002/essoar.10505899.1
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发表时间：
2021
期刊：
--
影响因子：
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通讯作者：
Brown M
Brown M
中科院分区：
--
文献类型：
--
作者：
Brown M

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二氧化碳的增加会导致高层大气变冷，并随着时间的推移导致大气密度长期下降。通过使用具有热层和电离层延伸的整个大气群气候模型 (WACCM-X)，在二氧化碳浓度增加的情况下模拟了长达 500 公里的中性热层密度。模拟之间仅改变二氧化碳和一氧化碳浓度，并且太阳活动自始至终保持在 F10.7 = 70 的低水平。使用政府间气候变化专门委员会 (IPCC) 制定的四种代表性浓度路径 (RCP) 二氧化碳情景，对到 2100 年中性密度下降的情景进行了建模。还模拟了 1975 年和 2005 年，这表明中性密度每十年变化 -5.8% 的历史趋势。相对于 2000 年，中性密度有所下降，原因是地面二氧化碳浓度增加。 WACCM-X 显示，与 2000 年的密度相比，400 公里处的中性密度已经下降了 17%。根据《巴黎协定》中规定的将升温限制在 1.5 摄氏度的 50:50 概率阈值，这意味着下降了 30%。一个简单的轨道传播器已被用来显示密度下降对穿过热层的物体的轨道寿命的影响。如果实现 1.5 摄氏度的目标，LEO 中物体的轨道寿命将比 2000 年的同类物体长约 30%。
Increasing carbon dioxide causes cooling in the upper atmosphere and a secular decrease in atmospheric density over time. With the use of the Whole Atmospheric Community Climate Model with thermosphere and ionosphere extension (WACCM-X), neutral thermospheric densities up to 500 km have been modelled under increasing carbon dioxide concentrations. Only carbon dioxide and carbon monoxide concentrations are changed between simulations, and solar activity is held low at F10.7 = 70 throughout. Using the four Representative Concentration Pathway (RCP) carbon dioxide scenarios produced by the Intergovernmental Panel on Climate Change (IPCC), scenarios of neutral density decrease through to the year 2100 have been modelled. The years 1975 and 2005 have also been simulated, which indicated a historic trend of -5.8% change in neutral density per decade. Decreases in the neutral density relative to the year 2000 have been given for increasing ground-level carbon dioxide concentrations. WACCM-X shows there has already been a 17% decrease in neutral densities at 400 km relative to the density in the year 2000. This becomes a 30% reduction at the 50:50 probability threshold of limiting warming to 1.5 degrees Celsius, as set out in the Paris Agreement. A simple orbital propagator has been used to show the impact the decrease in density has on the orbital lifetime of objects travelling through the thermosphere. If the 1.5 degrees Celsius target is met, objects in LEO will have orbital lifetimes around 30% longer than comparable objects from the year 2000.