Multiple Satellite Analysis of the Earth’s Thermosphere and Interplanetary Magnetic Field Variations Due to ICME/CIR Events During 2003–2015

We present a refined statistical analysis based on interplanetary coronal mass ejections (ICMEs) as well as corotating interaction regions (CIRs) for the time period 2003–2015 to estimate the impact of different solar wind types on the geomagnetic activity and the neutral density in the Earth’s thermosphere. For the time-based delimitation of the events, we rely on the catalog maintained by Richardson and Cane and the corotating interaction region lists provided by S. Vennerstrom and Jian et al. These archives are based on in situ measurements from the Advanced Composition Explorer and/or the Wind spacecraft. On this basis, we thoroughly investigated 196 Earth-directed ICME and 195 CIR events. To verify the impact on the Earths thermosphere we determined neutral mass densities by using accelerometer measurements collected by the low-Earth-orbiting satellites Gravity Recovery and Climate Experiment and Challenging Minisatellite Payload. Subsequently, the atmospheric densities are related to characteristic ICME parameters. In this process a new calibration method has been examined. Since increased solar activity may lead to a decrease of the satellites orbital altitude we additionally assessed the orbital decay for each of the events and satellites. The influence of CIR events is in the same range of magnitude as the majority of the ICMEs (186 out of 196). Even though, the extended investigation period between 2011 and 2015 has a lack of extreme solar events the combined analysis reveals comparable correlation coefficients between the neutral densities and the various ICME and geomagnetic parameters (mostly >0.85). The evaluation of orbit decay rates at different altitudes revealed a high dependency on the satellite actual altitude.