Transition radiation from relativistic intergalactic dust grains

Transition radiation is emitted when a charged particle traverses a boundary separating two media. Such radiation must therefore be emitted as X-rays and ultraviolet radiation, from a medium where cosmic-ray electrons pass through dust grains. Calculation shows that transition radiation emitted in this way might account for soft X-rays emission from relativistic charged dust grains in the intergalactic medium (IGM). This could be a help in understanding the IGM as well as an indirect method of measuring the energies of high energy particles.