Modelling the Radio Emission of Inclined Air Showers in the 50-200 MHz Frequency Band for GRAND

The Giant Radio Array for Neutrino Detection (GRAND) is a distributed, sparse ground antenna array designed to detect the radio emission from highly inclined extensive air showers induced by ultra-high-energy particles in the atmosphere. We use CoREAS air-shower simulations to adapt an existing signal model of the radio emission of inclined showers to the 50 − 200 MHz frequency band GRAND is sensitive to. The model uses a parameterisation of the charge excess emission to isolate the geomagnetic component. By fitting a one-dimensional lateral distribution function to the geomagnetic energy fluence of a shower, we reconstruct its radiation energy. This work details the signal model and the intrinsic event reconstruction of our method, as well as the adaptations to the new frequency band. This work is part of the NUTRIG project.