Radio-detection of neutrino-induced air showers: influence of topography

Neutrinos of astrophysical origin could be detected through the electromagnetic radiation of the particle showers induced in the atmosphere by their interaction in the Earth. This applies in particular for tau neutrinos of energies E$> $10$^{16}\,$eV following Earth-skimming trajectories. The $\sim 1 \deg$ beaming of the radio emission in the forward direction however implies that the radio signal will likely fly above a detector deployed over a flat site and would therefore not be detected. We study here how a non-flat detector topography can improve the detection probability of these neutrino-induced air showers. We do this by computing with three independent tools the neutrino detection rate for a radio array deployed over a toy-model mountainous terrain. We show that ground topographies inclined by few degrees only induce detection rate as high as 6 times larger than those obtained for flat areas. We conclude that the topography of the area where the detector is deployed will be a key factor for an experiment like GRAND