Non-thermal or synchrotron radiation is most common from of radio emission which is associated with relativistic electrons. These radiations are emitted when the relativistic electrons encounter a magnetic field and spiral around it. Since the spiral is continuously changing the direction of the electron, it is in effect accelerating and emitting radiation.
The synchrotron radiation of the non-thermal radio sources affects it's behavior at low radio frequencies due to several effects e.g. synchrotron self absorption, Razin-Tsytovich effect etc. The spectra of the radio sources can be studied which is the main source of information regarding the physical processes inside them.