Coherent radio emission from the cosmic ray air shower sudden death

We describe the characteristics of a new radio signal, generated by the secondary electrons and positrons of the shower front when they reach the ground. The very fast deceleration of these particles induces the coherent emission of an electric field at frequencies smaller than 20 MHz. We show, using simulations with the code SELFAS, that this sudden death signal should be detectable with a simple dedicated antenna and could provide many informations on the shower, in particular the nature of the primary cosmic ray. We also show that this signal permits to estimate the atmospheric depth of maximum of electric field emission X_{max}^{prod}, which occurs max well before the atmospheric depth corresponding to the maximum number of secondary particles in the shower (Xmax). Observation of this signal should be considered for the design of future radio experiments.