Recent results from the Yakutsk experiment: The development of EAS and the energy spectrum and primary particle mass composition in the energy region of 1015–1019 eV

Experimental data obtained at the Yakutsk array after the modernization in 1993 are analyzed. The characteristics of EAS longitudinal and radial development found from the charged particle flux and EAS Cerenkov light registered at the Yakutsk array complex are presented. The energy spectrum of EAS obtained from Cerenkov light and an estimate of the mass composition of primary cosmic rays are presented.