A. V. Sabourov

The spectrum features of UHECRs below and surrounding GZK

The energy spectrum of ultra-high energy cosmic rays (UHECRs) is discussed on the basis of the Yakutsk array database analysis. In the region E 0 = 10 17 to 3 × 10 19 eV the showers are detected under trigger-500, while at energies above 3 × 10 19 eV the whole acceptance area for trigger-1000 is used in order to utilize all the data available in the region of Greisen-Zatsepin-Kuzmin (GZK) cutoff. Updated relations are adapted to estimate the primary energy having detected densities of charged particles at the distance 300/600 m from the shower axis.

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.

SPECTRUM OF COSMIC RAYS WITH ENERGY ABOVE 1017 EV

The energy spectrum of primary cosmic rays with ultra-high energies based on the Yakutsk EAS Array data is presented. For the largest events values of S600 and axis coordinates have been obtained using revised lateral distribution function. The effect of the arrival time distribution at several axis distance on estimated density for Yakutsk and AGASA is considered.

Atmospheric monitoring at the Yakutsk EAS array

There are several instruments at the Yakutsk EAS array which are used for monitoring of atmospheric conditions. Here we present the results of perennial observations of the atmospheric spectral transparency, seasonal variations of aerosol optical depth, stratospheric temperature and ground-level electric field. These characteristics are used during the processing of primary data obtained by the EAS array.