Global Electron Content and Neutral Density of the Thermosphere at Launches in 2019–2023

In order to avoid emergency situation it is necessary to take into account impact of disturbances in space environment during launch of space vehicles. This paper examines changes in the neutral density of the thermosphere (ρ) according to satellites and global electron content (GEC) from JPL GIM-TEC maps during 130 satellite launches in 2019-2023. The variations of ρ and GEC over the 24-hour period centered at the launch time were identified and analyzed. The spatial distribution and evolution of ρ and GEC in terms of solar activity, season and level of geomagnetic activity before and after each launch event were investigated. It is shown that with increasing the phase Φ of the solar cycle (SC) from Φ = 0.5 (February 2022) to a maximum Φ = 1 (April 2024) of SC25, the value of by 2.1 and 3.5 times, respectively. During this period, 75 magnetic storms of categories NOAA G1–G4 were observed at ≥ 5.0, of which 19 storms has occurred in the interval ±24 hours from the moment of launch. Only in one case an emergency was observed on February 3, 2022, during the launch of , when 38 out of 49 satellites left orbit during a minor two-phase geomagnetic storm of level G1 ( = 5.3). Comparison is made with another successful launch on March 23, 2023 during an intense magnetic storm of category G3 ( = 7.3). It is shown that at the launch the neutral density ρ prevailed in the northern high latitudes, while in the case of , the thermosphere was denser near the equator. After launch, the transition from the positive to negative perturbation of GEC has happened while a strictly negative GEC anomaly was observed in the case of . The examples considered show that the intensity of a geomagnetic storm is not the only criterion for an emergency situation. Other characteristics should be taken into account when launching spacecraft, including an increase in electron content in the ionosphere and the density of the neutral atmosphere, accompanied by increased satellites drag at low orbits.