cyclotron radiation

Cyclotron radiation is a type of radiation that is emitted by a charged particle if accelerated and at less than relativistic speed. Such acceleration is generally in magnetic fields, in which such particles can travel in spiraling orbits (reminiscent of a coil spring), a phenomenon which can occur in magnetic fields in space. Cyclotron radiation characteristics:

• A spike in the spectrum at the frequency of the particle's orbit, i.e., the cyclotron frequency.
• Harmonics of this spike at integer multiples of its frequency.
• Polarization characteristics dependent upon the directions of observation and of the magnetic field.

The period of the particle's orbit is inversely proportional to the magnetic field strength, making such radiation a means detecting characteristics of magnetic fields. The name cyclotron radiation stems from its appearance in a type of particle accelerator termed a cyclotron.

The orbits of electrons within atoms fail to produce such radiation, one of the oddities that led to the development of quantum theory.

Analogous radiation from near-light-speed charged particles is called synchrotron radiation.