With the successful launch of the satellite mission Gravity Recovery and Climate Experiment (GRACE) Follow‐On in May 2018 the opportunity arises to resume the analysis of accelerometer data regarding space weather induced perturbations of the Earth's thermosphere. On 21 August 2018 a complex interplanetary coronal mass ejections occurred on the Sun, which subsequently triggered an unexpected large geomagnetic storm on 26 August. We present a detailed analysis of the interplanetary coronal mass ejection eruption and explore the occurred perturbation of the neutral mass density in the upper Earth's atmosphere. Due to the heating and the subsequent expansion of the thermosphere also the drag force acting on the spacecraft is enhanced. This leads to an additional storm‐induced orbit decay, which we calculate by means of variations in the semimajor axis. The evaluation is based on the utilization of accelerometer measurements from GRACE Follow‐On. For the reduction of disturbing nongravitational forces we implemented a physical shadow function, which incorporates the Earth's oblateness and the atmospheric refraction and extinction. Additionally, the estimation of Earth's reradiation is now based on hourly measurements by the Clouds and the Earth's Radiant Energy System. The resulting atmospheric densities and orbit decays are compared with predictions from our preliminary thermospheric forecasting tool, which is based on the study by Krauss et al. (2018, https://doi.org/10.1029/2018JA025778). The evaluation shows that the maximum estimated orbit decay triggered by the geomagnetic storm on 26 August is in the order of approximately 8.2 m and thus in good accordance with the forecasted value (9.5 m)—predicted with a lead time of about 60 min.

中文翻译：

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使用GRACE追踪数据探索2018年8月26日严重地磁风暴触发的热层变化

随着卫星任务重力恢复和气候实验（GRACE）的成功发射，于2018年5月启动，有机会继续进行关于空间天气引起的地球热层扰动的加速度计数据分析。2018年8月21日，太阳上发生了复杂的行星际日冕物质抛射，随后在8月26日引发了意外的大地磁风暴。我们对行星际日冕物质喷发进行了详细分析，并探讨了地球上层大气中中性物质密度发生的扰动。由于热圈的加热和随后的膨胀，作用在航天器上的阻力也增加了。这导致了额外的风暴诱发的轨道衰减，我们通过半长轴的变化来计算。评估是基于GRACE Follow-On对加速度计测量值的利用。为了减少干扰性的非引力，我们实现了物理阴影功能，该功能结合了地球的扁率和大气折射和消光。此外，现在对地球辐射的估算是基于云和地球辐射能系统每小时进行的测量。将由此产生的大气密度和轨道衰减与我们初步的热层预报工具的预测进行比较，该工具是基于Krauss等人的研究得出的。（2018，https://doi.org/10.1029/2018JA025778）。