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High-energy interactions of cosmic γ rays and protons with the earth atmosphere have been simulated by means of the CORSIKA Monte Carlo code, and the secondary particle density distributions at ground level in the resulting extensive air showers have been studied. It is shown that the power spectrum of the bidimensional particle density fluctuations have features typical of a 1/f noise in the bidimensional frequency domain, and is found to have different features for different primary cosmic rays. This property is applied to the separation of electromagnetic from proton simulated extensive air showers and it is proposed as a new discrimination method that can be used experimentally for real-time γ–proton separation. A cutting parameter related to the bidimensional power spectrum is calculated and the efficiency of the cutting procedure for γ–proton separation is evaluated. [Copyright &y& Elsevier]

High-energy interactions of cosmic γ rays and protons and also helium, oxygen and iron nuclei with the Earth atmosphere have been simulated by means of the CORSIKA Monte Carlo code, and the secondary-particle density distributions at ground level in the resulting extensive air showers (EAS) have been studied. It is shown that the fluctuations of the particle density distributions have features typical of a 1/f noise. The multifractal spectrum of the samples is obtained and is found to have different features for different primary cosmic rays. This property is applied to the separation of electromagnetic from hadronic simulated EAS and it is proposed as a discrimination method when real data are available. A cutting parameter related to the multifractal spectrum is calculated and the efficiency of the cutting procedure for γ-hadron separation is evaluated. [Copyright &y& Elsevier]