Generation of the auroral kilometric radiation
Data collected from the S3-3 spacecraft in the auroral kilometric radiation (AKR) source region are employed to form a stability theory from which numerical results are obtained and discussed. The distribution function was found to be isotropic outside the auroral atmospheric loss-cone region, which was partially filled with upcoming electrons. A parallel electric field was observed to be modifying the loss-cone distribution. A model distribution function is formulated, along with a magnetic field model expressed in terms of the electron cyclotron frequency. Models for the parallel electric field are also introduced, the first with the field distributed over a broad altitude range, while the second assumes a potential drop only above 4000 km. The presence of the field is found to enhance the growth rate of the AKR. At higher altitudes, the cutoff frequency of the X mode is affected by the rising energetic electrons. Finally, the folding distances of spatial amplification are calculated.