Atmospheric infrasound disturbances during the large 2013 May 22 solar energetic particle event

The paper presents research on atmospheric infrasound disturbances during large solar energetic particle event on 2013 May 22. This event is remarkable for its interacting coronal mass ejections, which caused a high level of particle intensity, that reached the value of 2740 $c{m}^{-2}{s}^{-1}s{r}^{-1}$ in the $>$1 MeV GOES energy channel respectively according to NOAA GOES data. The maximum energetic particle flux occurred at 08:20 UT on 05/23/2013 and about three hours after that, we registered the beginning of the daily cycle disturbance of natural atmospheric infrasound with a duration of up to 2 days and an increase in the magnitude of infrasound by $\sim 3÷$4 times. A probable mechanism of infrasound generation is proposed. The observed value of the time delay of infrasound arrival in relation to the moment of generation of energetic protons consists mainly of the infrasound propagation time from high latitudes to the observatory and is counted from the moment the peak flux of lower-energy protons arrives. It is found that before the disturbance, the spectrum of the atmospheric infrasound signal was dominated by oscillations with a period of $T\approx 300$ s, while after the disturbance, the width of the infrasound frequency spectrum increased and oscillations with periods of $T\approx 100÷230$ s became dominant. The correlation of the proton flux density and the infrasound amplitude with the electric field strength in the surface atmosphere is revealed and explained.