Ionospheric F₂ region perturbed by the 25 April 2015 Nepal earthquake

Seismic waves can be detected in the Earth's atmosphere and ionosphere; however, their impacts on ionospheric electron density (Ne) structures near the altitude of peak Ne (h_mF₂) have not yet been fully determined due to the lack of sufficient observations sampled in the vertical direction. Here we apply a ground-based Global Positioning System (GPS) receiving network in Asia as well as the space-based GPS occultation experiment on board the FORMOSAT-3/COSMIC (F3/C) satellite to vertically scan the ionospheric Ne structures, which were perturbed by the magnitude M_w7.8 Nepal earthquake that occurred on 25 April 2015. The F3/C altitudinal Ne profiles show that the Nepal earthquake-induced air perturbations penetrate into the ionosphere at supersonic speeds of approximately 800 m/s and change the Ne structure by 10% near h_mF₂. The vertical scale of the Ne perturbation is 150 km, while the h_mF₂ is uplifted by more than 30 km within 1 min. Those results reveal that the earthquake-induced ground displacement should be considered as a significant force that perturbs the vertical Ne structure of the ionosphere.