We show that coherent transition radiation from the electrically neutral transverse geomagnetic current (CTR-GM) in a cosmic-ray air shower provides a natural, standard model, explanation to the recent “anomalous” events observed by the ANITA detector. We demonstrate that for zenith angles less than $\sim 70°$, combined with high surface elevation, the inclusion of CTR-GM can significantly alter the emitted electric field from a cosmic-ray air shower. CTR-GM therefore has to be included in the radio emission models to provide a full description of the radio emission from a high-energy cosmic-ray air shower traversing a dielectric boundary.

• Received 30 March 2019
• Revised 8 June 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.091102