  Cosmic rays are messengers from highly energetic events in the Universe.
These rare ultra-high-energy particles can be detected efficiently and in an
affordable way using large arrays of radio antennas. Linearly polarized
geomagnetic emission is the dominant emission mechanism produced when charged
particles in air showers get deflected in the Earth's magnetic field. The
sub-dominant Askaryan emission is radially polarized and produced due to the
time-varying negative-charge excess in the shower front. The relative amplitude
of these two emission components depends on various air shower parameters, such
as the arrival direction and the depth of the shower maximum. We studied these
dependencies using CoREAS simulations of the radio emission from air showers at
the South Pole using a star-shaped antenna layout. On the one hand, the
parametrization of the Askaryan-to-geomagnetic ratio can be used as input for a
more accurate reconstruction of the shower energy. On the other hand, if
measured precisely enough, this ratio may provide a new method to reconstruct
the atmospheric depth of the shower maximum.

High Energy Astrophysical Phenomena