We introduce a semi-analytical framework to compute coherent pulses from extensive air showers initiated by cosmic rays inspired in previous work on modeling Askaryan radiation in dense media (ARVZ model). The predictions are benchmarked against detailed Monte Carlo simulations performed with the ZHAireS package. Our method accurately reconstructs the vector potential in the time domain and, consequently, the electric field in both the time and frequency domains for arbitrary observer locations on the ground. We show that the semi-analytical approach reproduces the expected radio signal with a precision better than 10% in the frequency band 30-80 MHz.
The technique is computationally efficient, requiring only the longitudinal profiles of the total and excess charge of the shower, along with a parameterized description of the vector potential at the location at which shower maximum is seen in the Cherenkov angle. Both inputs can be obtained from ZHAireS simulations. These results are directly applicable to the interpretation of data from current radio-based air-shower experiments, as well as to the design and optimization of future cosmic-ray and neutrino detection efforts.