  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.
