To study the nature of particles with energies greater than 5 EeV, the database of the Yakutsk array was analyzed. Showers coming one after the other are highlighted within a time interval of 1-20 hours. Some periodicity was found in the registration of such showers during the daily observation cycle with an average time of T = 8 hours. The characteristics of the selected showers: energy, zenith and azimuthal angles were found to be close in magnitude. Consequently, we can assume the same origin nature of the primary particles that initiate such showers. Existing discrepancy in the arrival time of showers at the Earth’s level can be attributed to the participation in various processes in outer space: the interaction of particles with different charges with galactic magnetic field, acceleration of particles due to the frictional mechanisms followed by re-emission with higher energy. And time delay at the shock front. If this hypothesis is correct, then the analysis of such air shower events will make it possible to obtain information on the processes of interaction of shock waves with the matter of the Universe.