Multiphoton cyclotron resonance absorption of laser radiation

The laser heating of plasma electrons in a uniform static magnetic field via the inverse bremsstrahlung process is considered. A kinetic equation is derived, and the change in kinetic energy of the electrons is calculated. For laser radiation propagating parallel to the magnetic field and incident on cold electrons, it is found that multiphoton processes are dominant when the laser frequency is near the electron cyclotron frequency. The multiphoton absorption coefficient is found to decrease as the laser frequency approaches the electron cyclotron frequency. The presence of the magnetic field reduces the intensity threshold above which multiphoton absorption occurs.