Radio emission from ultra-high energy cosmic-ray showers after reflecting on the Earth.

We present the calculation of coherent radio pulses emitted by extensive air showers induced by ultra-high energy cosmic rays accounting for reflection on the Earth’s surface. Our work is motivated by the detection of pulsed events in the ANITA experiment compatible with cosmicray origin after reflection on the ice cap at the South Pole. The properties of the radiation are discussed in detail emphasising the effects of reflection on the intensity, frequency and angular distribution of the signal. Our results are obtained with a new version of the ZHAireS simulation code, accounting for reflection on a surface. These calculations are of relevance in studies of existing and future radio detection experiments looking at the Earth from mountain tops, balloons and satellites.