Distribution of maximum depths of extensive air showers (EAS) with energies of 1017–1018 eV is restored from the lateral distribution of EAS radio emission measured by the LOPES experiment (40-80 MHz). Dependence of the EAS maximum depth on its energy is constructed and mass composition of cosmic rays is estimated. It follows from the obtained dependencies that the fraction of light cosmic ray's nuclei increases in the energy range under consideration.

Experimental data obtained for the lateral distribution of radio emission from extensive air showers (EAS) at the array of Moscow State University (30–34 MHz) and the LOPES array (40–80 MHz) were comparedwith the results of calculations performed within amicroscopic approach based on aMonte Carlo simulation of EAS (CORSIKA code). The same experimental data were used to reconstruct the distribution of the depth of the EAS maximum at cosmic-ray energies in the range of 1017–1018 eV. The energy dependence of the depth of the EAS maximum was constructed for the case of data from the LOPES array, and the mass composition of cosmic rays was estimated for this case. From the resulting dependences, it follows that the mass composition shows a trend toward becoming lighter in the energy range being considered

Experimental data obtained for the lateral distribution of radio emission from extensive air showers (EAS) at the array of Moscow State University (30–34 MHz) and the LOPES array (40–80 MHz) were comparedwith the results of calculations performed within amicroscopic approach based on aMonte Carlo simulation of EAS (CORSIKA code). The same experimental data were used to reconstruct the distribution of the depth of the EAS maximum at cosmic-ray energies in the range of 1017–1018 eV. The energy dependence of the depth of the EAS maximum was constructed for the case of data from the LOPES array, and the mass composition of cosmic rays was estimated for this case. From the resulting dependences, it follows that the mass composition shows a trend toward becoming lighter in the energy range being considered

This work compares the experimental data on the lateral distributions of radio emissions from extensive air showers (EAS) measured with the MSU and LOPES experiments to calculations performed within the microscopic approach based on a Monte Carlo simulation of EASes (the CORSIKA code).

The results of a reanalysis of experimental data on extensive-air-shower radioemission that were obtained previously at the Moscow State University array for studying extensive air showers are presented. The lateral distribution of radioemission is given for showers characterized by a primary energy of 4 × 1017 eV and a zenith angle of θ = 35°. On the basis of an analysis of a lateral distribution of radioemission, the average value of the shower-maximum depth at a primary energy of 4 × 1017 eV is estimated at X max = 655 ± 13 g/cm2. Estimates of themass content of primary radiation that were obtained from an analysis of the distribution of X max are compatible with the hypothesis that the role of light nuclei becomes more pronounced at energies above 1017 eV.

The results of a reanalysis of experimental data on extensive-air-shower radioemission that were obtained previously at the Moscow State University array for studying extensive air showers are presented. The lateral distribution of radioemission is given for showers characterized by a primary energy of 4 × 10 17 eV and a zenith angle of θ = 35°. On the basis of an analysis of a lateral distribution of radioemission, the average value of the shower-maximum depth at a primary energy of 4 × 10 17 eV is estimated at X max = 655 ± 13 g/cm 2 . Estimates of themass content of primary radiation that were obtained from an analysis of the distribution of X max are compatible with the hypothesis that the role of light nuclei becomes more pronounced at energies above 10 17 eV.

The results of the reprocessing of the experimental data on radio emission from extensive air showers (EAS) earlier obtained at the EAS facility (Moscow State University) are reported. The maximum depth distribution of showers is found from analysis of the width of the spatial distribution of radio emission. The average maximum depth is X max = 655 ± 8 g/cm2 for the primary particle energy E 0 ∼ (3–4) × 1017 eV. The normalized field strength at E 0 = 1017 eV is 3.2 ± 0.6 and 2.8 ± 0.4 μV/(m MHz) at distances of 50 and 100 m from the axis, respectively. The accuracy of E 0 determination from the radio emission field strength at 50 m from the axis is about 20%.

The project of a new complex array for super-high energy (> 10 eV) cosmic ray research is considered. The new array will be constructed on the basis of the EAS MSU array. It will be modified and extended by new scintillation detectors located at 1–2 km from the center of EAS MSU array. Neutron and Cherenkov detectors will be added to the scintillation detector system.

We have analysed arrival times of extensive air showers (EAS) registered with the EAS-1000 prototype array during the period from August, 1997 till February, 1999. Our analysis has revealed that though the vast majority of samples of consecutive time intervals between EAS arrival times obey the exponential distribution, there are sequences of showers that have another distribution and thus violate the homogeneity hypothesis. The search for correlation between such events and clusters of showers and events with big delays between arrival times was also carried out.

The status of EAS:-1000 array is presented. Considering the possibility of data acquisition on EAS muons and Cherenkov light the problem of CR mass composition investigations is discussed.

At the Moscow University EAS array the detector pulse shapes were observed with the help of two scintillation detectors of area 4 , each separated by 23 m. The pulse shapes were analysed in EAS with a particle density of more than 10 . 13 pulses were observed in the EAS with sizes at core distances R > 200 m. Some of the pulses have fine temporal structure with secondary peaks corresponding to tens of particles. Comparison of the individual experimental pulse shapes with the pulse shapes expected for the EAS particles arriving randomly due to the average time distribution indicates the non-statistical temporal structure of the pulses.