Air showers and geomagnetic field

The influence of the geomagnetic field on the development of air showers is studied. The well known International Geomagnetic Reference Field was included in the AIRES air shower simulation program as an auxiliary tool to allow the calculation of very accurate estimations of the geomagnetic field given the geographic coordinates, altitude above sea level and date of a given event. Our simulations indicate that the geomagnetic deflections significantly alter some shower observables such as, for example, the lateral distribution of muons in the case of events with large zenith angles (larger than 75 deg.). On the other hand, such alterations seem to be unimportant for smaller zenith angles. Global observables such as the total number of particles or longitudinal development parameters do not present appreciable dependences on the geomagnetic deflections for all the cases that were studied. (author)