Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory

TL;DR

This study investigates how atmospheric variations like pressure and density influence the development and detection of extensive air showers caused by cosmic rays, using data from the Pierre Auger Observatory.

Contribution

It provides a validated model linking atmospheric parameters to air shower characteristics, improving understanding of atmospheric effects on cosmic ray observations.

Findings

Event rate varies seasonally by ~10% and daily by ~2%.

Pressure affects the longitudinal development of air showers.

Density influences the lateral distribution of shower particles.

Abstract

Atmospheric parameters, such as pressure (P), temperature (T) and density, affect the development of extensive air showers initiated by energetic cosmic rays. We have studied the impact of atmospheric variations on extensive air showers by means of the surface detector of the Pierre Auger Observatory. The rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find that the observed behaviour is explained by a model including the effects associated with the variations of pressure and density. The former affects the longitudinal development of air showers while the latter influences the Moliere radius and hence the lateral distribution of the shower particles. The model is validated with full simulations of extensive air showers using atmospheric profiles measured at the site of the Pierre Auger Observatory.