Low energy cosmic ray physics with the Pierre Auger Observatory

The Pierre Auger Observatory was built to measure cosmic rays with the highest energies and lowest flux. For this purpose 1660 surface detectors cover an area of about 3000 km² and are overlooked by four telescope stations. Next to the high energy events, periodically also various non-event data are recorded for each of the surface detectors. These data are mainly used for hardware calibration and performance monitoring of the array. Nevertheless, they indirectly carry also interesting information about particles with energies in a MeV to GeV range and can therefore as well be used for physics analyses aimed at the low-energy part of the cosmic ray spectrum. The sensitivity of such analyses to small changes in rates of low-energy cosmic rays is due to the large statistics collected by the array of 1660 stations, each having an area of about 10 m². With these data we can for example observe changes in solar activity and Forbush decreases in the rate of low-energy cosmic rays.