CONCLUSIONS
Our ground level cosmic ray flux measurements show the modulation effects from both atmospheric and space weather parameters. Atmospheric influence is first removed in order to understand the solar modulation effect. Short-term cosmic flux measurements show an anti-correlation with atmospheric pressure and the barometric coefficient was found to be −0.13±0.01 %/mb. This barometric coefficient was used to correct the Pot detector data
for pressure. Pressure corrected cosmic data shows a seasonal variation with a significant drop of muon counts during the summer time while a higher counting rate seen in winter. This count variation occurs due to the fluctuation of primary particle interaction altitude as a result of seasonal temperature changes. The temperature coefficient for the Pot data was found to be −0.26%/◦C. Pressure corrected muon data also show the effect of solar
modulation due to coronal mass ejections.
To understand the atmospheric influence (effects of the tropospheric and stratospheric density variations) on cosmic flux, numerical simulations of cosmic muon and neutron flux variations at the surface of the earth have been carried out. Our simulation results show that the density variations in the troposphere mainly influence the neutron flux while its influence on the muon flux is relatively insignificant. On the other hand, variation of the stratospheric density dominates the muon flux which is in remarkably good agreement with observed seasonal variation of muon flux. It is, therefore, very important to have a long- term simultaneous monitoring of both cosmic ray muon and neutron flux on a global scale in order to study the dynamical change of the atmosphere. These results pave a new path for systematically studying the global temperature evolution using worldwide cosmic ray data.
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