Auroral kilometric radiation: A theoretical review

A number of theories have been proposed in recent years to explain auroral kilometric radiation. These include an anisotropic velocity distribution instability, mode conversion of electron cyclotron waves to ordinary mode radiation, soliton radiation, beam-driven instability of electromagnetic waves via low-frequency turbulence, a loss cone instability, beating of coherent electrostatic waves, and beam amplification of electromagnetic waves via coherent density fluctuations. These will all be reviewed, and comparisons of prediction made with observations. Emphasis will be placed on the three recent proposals