Directional Dependence of the Angular Resolution of a Radio Antenna Array due to the Earth’s Magnetic Field

Recent years have seen a growing interest in radio detection of Cosmic Rays. We investigated the incident direction of Cosmic Rays for an array of 11 radio antennas through a series of simulations using the CoREAS toolkit. We have determined that utilizing the east-west component of the electric field yields improved angular resolution for our array compared to the north-south and vertical components. Our findings reveal a significant correlation between the error in direction estimation of cosmic rays and the angle between the earth’s magnetic field and the cosmic ray’s trajectory. Specifically, for 1017 eV proton showers, we observe that the angular resolution is poorer for showers originating from the south (0.91°±0.06°) compared to those from the east (0.48±0.07), north (0.33°±0.08°), and west (0.30°±0.10°) directions. Additionally, a slight decrease (less than 0.1°) in angular resolution is noted for 1018 eV showers. This research sheds light on the impact of Earth's magnetic field on cosmic ray detection using radio antenna arrays.