Calculation Methods for Radio Pulses from High Energy Showers
  We present an approximation for the numerical calculation of Cherenkov radio pulses in the Fraunhofer limit from very high energy showers in dense media. We compare it to full Montecarlo simulations in ice studying its range of applicability and show how it can be extended with a simple algorithm. The approximation reproduces well the angular distribution of the pulse around the Cherenkov direction. An improved parameterization for the frequency spectrum in the Cherenkov direction is given for phenomenolgical applications. We extend the method to study the pulses produced by showers at distances at which the Fraunhofer limit does not apply, and give the ranges of distances and frequencies in which Fraunhofer approximation is good enough for interpreting future experimental data. Our results are relevant for the detection of very high energy neutrinos with this technique. 
J. Alvarez-Mu\~niz (U. of Wisconsin, Madison), R.A. V\'azquez, E. Zas   (U. of Santiago de Compostela, Spain)