ar X iv : a st ro - p h / 06 09 80 9 v 1 2 9 Se p 20 06 Geosynchrotron radio emission from CORSIKA - simulated air showers

Simulations of radio emission from extensive air showers we have published so far were performed with a Monte Carlo code using analytical parametrisations to describe the spatial, temporal, energy and angular particle distributions in the air shower. A new version of our simulation code, which replaces these parametrisations with precise, multi-dimensional histograms derived from per-shower CORSIKA simulations, is now available. The new code allows an independent selection between parametrisation and histogram for each of the relevant distributions, enabling us to study the changes arising from using a more realistic air shower model in detail. We describe the new simulation strategy, present some initial results and discuss the new possibilities. 1. Introduction In the past few years, we have modelled geosynchrotron radio emission from extensive air showers with both analytic calculations [1] and extensive Monte Carlo simulations [2], the results of which have been presented and summarised in a parametrisation formula in [3]. These Monte Carlo simulations were based on an air shower model using analytical parametrisations (see [1]) to describe the spatial, temporal, energy and angular distributions of the air shower particles. The new Monte Carlo code presented here replaces these analytical parametrisations with multi-dimensional histograms generated for each individual shower by the air shower simulation code CORSIKA [4], allowing a much more precise calculation of the radio signal. In the following, we present the new simulation strategy before discussing a few examples of the effects arising as a consequence of the transition to the realistic, histogrammed particle distributions and the elimination of the track length parameter that was present in the earlier simulations. Afterwards, we discuss some examples of how the new code can be used to explain the shape of the emitted radio pulses, followed by our conclusions.