bremsstrahlung
From Glossary of Meteorology
Electromagnetic radiation resulting from the acceleration or deceleration of subatomic particles such as electrons when they interact with matter; often applied to the continuous part of the x-ray spectrum produced when high-energy electrons bombard a material.
Bremsstrahlung is German for "braking radiation." In cosmic ray shower production, bremsstrahlung gives rise to emission of gamma rays as electrons encounter atmospheric nuclei.