Numerical analysis of double layers in the downward current region of the aurora

On the basis of two magneto-fluid model for two time-scales, the evolution of double layer in the downward current region of the aurora is numerically simulated under the non-static limit case. The results show that localized drop in density owing to collapsed high-frequency field can lead to the formation of double layer. The amplitude of the double layer is the order of the electron temperature, and the ramp potential is up to 36 V localized to tens of Debye lengths, which is around 100-200 m. These are consistent with the measurements in both the ramp potential and thickness by the Fast Auroral SnapshoT satellite in the downward current region of the aurora.