Ionospheric perturbations over central Europe caused by the Kamchatka M8.8 earthquake on 29 July 2025.

We present observations and analysis of co-seismic infrasound in the ionosphere recorded by continuous Doppler sounding over Czechia and associated with the Kamchatka M8.8 earthquake on July 29 2025. The co-seismic infrasound was observed at a height of almost 340 km, which is much higher (by more than 100 km higher) than in previous Doppler sounding observations of co-seismic infrasound, for example, observations in Czechia associated with Tohoku 2011, Nepal 2015 or Turkey 2023 earthquakes. It is also shown that only long period waves (around 3 min) from the initial wave spectrum were able to reach such a high altitude. The initial wave spectrum of vertical ground surface motion that generated the infrasound waves was much broader, including more intense fluctuations at periods around 20 s, but these shorter period waves were attenuated below the altitude of observation. The observation is consistent with numerical simulations of infrasound propagation.