Theory of electromagnetic waves on auroral field lines.

Abstract

Intense bursts of electromagnetic radiation generated in auroral regions during substorms radiate as much as one percent of the precipitated electron energy. The generation mechanism for the intense bursts of radio noise is apparently associated with the auroral electron beam. Some processes suggested for direct generation of electromagnetic noise by the auroral electron beam are briefly reviewed but it is suggested that the electromagnetic noise bursts are created indirectly due to radiation from strong electrostatic turbulence generated by the auroral electron beam. Due to refraction of ray paths out of the spatially limited auroral electron beam, beams below a certain intensity generate low levels of electrostatic noise as commonly observed by polar orbiting satellites. However, above a certain level, the electrostatic noise generated by the beam becomes intense and forms ‘solitons’ (large ion density cavities) or ‘spiky turbulence.’ Soliton turbulence can radiate efficiently enough to account for the observed levels of electromagnetic radiation.