  Cosmic ray air showers are known to emit pulsed radio emission at frequencies
around a few tens of MHz. Accompanying the experimental efforts of the LOPES
project, situated at the KASCADE-Grande site of the Forschungszentrum
Karlsruhe, we have modeled the underlying emission mechanism in the scheme of
coherent geosynchrotron radiation from electron-positron pairs deflected in the
earth's magnetic field. As a follow-up to our earlier analytical calculations,
we have developed a Monte Carlo simulation based on analytic parametrisations
of air shower properties, including longitudinal and lateral particle
distributions, particle energy and track-length distributions, and the
longitudinal shower development as a whole. Here we present detailed simulation
results. Important findings are the absence of significant asymmetries in the
total field strength emission pattern in spite of the asymmetry introduced by
the geomagnetic field, the polarisation characteristics of the geosynchrotron
emission, allowing an unambiguous test of the geomagnetic emission mechanism,
and the dependence of the radio emission on important shower parameters such as
the shower zenith angle, the primary particle energy and the depth of the
shower maximum. As a particularly useful result, these dependences have been
summarized in a simple parametrisation formula, providing a solid basis for the
interpretation of experimental data gathered with current and future
experiments.
