Heating of a magnetically confined plasma that provides energy to ions through high frequency electromagnetic radiation. An ion orbiting with a certain frequency around a magnetic field line is able to absorb energy from radiation of the same frequency. Radiation at a frequency of tens of MHz increases the energy of the ions in the plasma, which pass it on to the electrons by collisions. Ion cyclotron resonance heating is used in tokamaks and stellarators to provide external heating of the plasma to fusion temperatures.