Cyclotron maser instability as a source of Auroral Kilometric Radiation

This paper is exploring Auroral Kilometric Radiation modelling it as a cyclotron maser emission from a horseshoe type instability. It corresponds to a horseshoe or crescent shaped momentum distribution of energetic electrons moving into the convergent magnetic field which exists around polar regions of dipole type stars and planets including the Earth. We have established a laboratory-based facility that has verified many of the details of our original theoretical description and agrees well with numerical simulations. Particularly, the horseshoe distribution was demonstrated to produce cyclotron emission at a frequency just below the local cyclotron frequency, with polarisation close to X-mode and propagating nearly perpendicularly to the beam motion. We also address a radiation escape problem and quasi-linear horseshoe distribution saturation.