电离层降水对地球热层NO生成及低轨卫星阻力的影响
The impact of electron precipitation on Earth's thermospheric NO production and the drag of LEO satellites
AI总结：
研究电离层降水对地球热层NO生成及低轨卫星阻力的影响，揭示其对卫星轨道预测模型的重要性。
摘要：
我们研究了空间天气事件对极地地区地球高层大气的响应，通过研究其对CHAMP和GRACE卫星阻力的影响。增加的太阳活动导致高层大气加热和膨胀，威胁低地球轨道（LEO）卫星。极光事件与太阳EUV辐射的恒星能量沉积和降水的高能电子密切相关，这些因素影响着如上层大气中一氧化氮（NO）生成等光化学过程。为了研究NO分子的生成及其对热层结构和卫星阻力的影响，我们首先用1D高层大气模型Kompot对地球背景热层进行建模，考虑了选定空间天气事件期间的X射线、EUV和红外辐射。为了研究极光中电子降水对极地热层中NO分子生成的影响，我们应用了考虑极光电子与周围N₂-O₂大气碰撞中随机碰撞散射的蒙特卡罗模型，包括超热N原子的生成。观测到的CHAMP和GRACE在两个研究事件中的大气阻力效应表明，极地热层中NO分子生成的偶发增强及其红外冷却能力，可以抵消热层膨胀并可能导致空间天气事件后密度下降的“过冷”现象，对LEO卫星具有保护作用。然而，其生成效率高度依赖于降水电子的能量通量。我们的结果对经验卫星轨道预测模型有直接意义，因为我们的模拟强调了考虑降水诱导的NO生成以提高这些模型预测能力的必要性。
英文摘要：
We investigate the response of space weather events on Earth's upper atmosphere over the polar regions by studying their effect on the drag of the CHAMP and GRACE satellites. Increasing solar activity that results in heating and the expansion of the upper atmosphere threatens low Earth orbit (LEO) satellites. Auroral events are closely related to the stellar energy deposition of solar EUV radiation and precipitating energetic electrons, which influence photochemical processes such as the production of nitric oxide (NO) in the upper atmosphere. To study the production of NO molecules and their influence on the thermospheric structure and satellite drag, we first model Earth's background thermosphere with the 1D upper atmosphere model Kompot by considering the incident X-ray, EUV, and IR radiation during selected space weather events. To investigate the effect of electron precipitation in the production of NO molecules in the polar thermosphere, we apply a Monte Carlo model accounting for the stochastic nature of collisional scattering of auroral electrons in collisions with the surrounding N$_2$-O$_2$ atmosphere, including the production of suprathermal N atoms. The observed effect of the atmospheric drag on CHAMP and GRACE during the two studied events indicates that a sporadic enhancement of NO molecule production in the polar thermosphere and its IR-cooling capability, which counteracts thermospheric expansion and can lead to an ``overcooling'' with decreased density after the space weather event, can have a protective effect on LEO satellites. Their production efficiency, however, is highly dependent on the energy flux of the precipitating electrons. Our results have direct implications for empirical satellite orbit prediction models, as our simulations highlight the need to consider precipitation-induced NO production to improve the predictive power of these models.
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