Dependence of the GRAPES-3 EAS particle density and trigger rate on atmospheric pressure and temperature

The GRAPES-3 experiment, a high-density extensive air shower (EAS) array located at Ooty, India is designed for high precision measurements of cosmic ray energy spectrum and nuclear composition in energy range of 10^13 - 10^16 eV . It consists of tightly packed 1 m 2 area 400 plastic scintillation detectors covering an effective area of 25,000 m^2. The trigger rate and particle density measured by EAS array shows strong correlation with the atmospheric parameters such as the pressure and temperature. By employing linear regression, and Fast Fourier Transform techniques, the pressure and temperature coefficients for the dependence of trigger rate and particle density, respectively were obtained. Thereafter, by applying corrections for these effects the contribution of atmospheric effects was largely eliminated in the EAS data. These corrections are expected to result in a better measurement of EAS parameters which will be presented during the conference.