We show that Abrikosov vortices moving towards the surface of a superconductor emit electromagnetic radiation into free space. The frequency distribution of the radiated intensity displays a pronounced maximum at microwave frequencies around v_x/lambda, where lambda is the magnetic penetration length. Coherent motion of a lattice of flux lines leads to constructive interference and increases the strength of the radiated power by a large factor.

4 pages, 1 figure The new version includes a derivation of novel dynamical London equations for a moving Abrikosov vortex, as well as a detailed discussion of boundary conditions