Radio Morphing: Fast computation of inclined air shower radio emission

The preparation of the next-generation of large-scale radio experiments requires running a large number of simulations to explore multiple detector configurations over vast areas and develop novel methods for the reconstruction of air shower parameters. While Monte Carlo simulations are accurate and reliable tools, they are too computationally expensive to explore the full parameter space of these new detectors within a reasonable timescale, and faster and more efficient methods are needed. We introduce a new version of Radio Morphing, a semi-analytical tool designed to simulate the radio emission of any cosmic-ray induced air shower with zenith angle θ>60, at any desired antenna position, from the simulation data of a few reference showers at given positions. This version incorporate refined scaling laws of the radio emission with the shower zenith angle, a novel interpolation method, the implementation of the charge-excess mechanism and the possibility to enable shower-to-shower fluctuations. We present the latest performances of Radio Morphing, tuned for a GRAND-like detector, which now provides an estimation of air shower radio signals four orders of magnitude faster than standard Monte Carlo simulations, while keeping an accuracy on the peak amplitude better than 17% on unfiltered traces, better than 13% in the [50 - 200] MHz band, and below about 10% in the [30 - 80] MHz band.