# Atmospheric aerosol attenuation effect on FD data analysis at the Pierre Auger Observatory

## TL;DR

This paper discusses how atmospheric aerosol measurements at the Pierre Auger Observatory are used to correct fluorescence detector data, improving the accuracy of cosmic ray shower analysis by accounting for aerosol attenuation effects.

## Contribution

It introduces a method to measure aerosol attenuation using laser facilities and validates its impact on the accuracy of cosmic ray data analysis.

## Key findings

- Aerosol attenuation correction improves energy estimation accuracy.
- Two measurement techniques for aerosol profiles are fully compatible.
- Uncertainty in aerosol profiles affects the precision of Xmax and energy measurements.

## Abstract

The atmospheric aerosol monitoring system of the Pierre Auger Observatory has been operating smoothly since 2004. Two laser facilities (Central Laser Facility, CLF and eXtreme Laser Facility, XLF) fire sets of 50 shots four times per hour during FD shifts to measure the highly variable hourly aerosol attenuation to correct the longitudinal UV light profiles of the Extensive Air Showers detected by the Fluorescence Detector. Hourly aerosol attenuation loads (Vertical Aerosol Optical Depth) are used to correct the measured profiles. Two techniques are used to determine the aerosol profiles, which have been proven to be fully compatible. The uncertainty in the VAOD profiles measured consequently leads to an uncertainty on the energy and on the estimation of the depth at the maximum development of a shower (X max ) of the event in analysis. To prove the validity of the aerosol attenuation measurements used in FD event analysis, the flatness of the ratio of reconstructed SD to FD energy as a function of the aerosol transmission to the depth of shower maximum has been verified.