Stepping into the Equatorward Boundary of the Auroral Oval: preliminary results of multi scale statistical analysis

This work aims at showing how analysis techniques, designed to highlight the multi-scale structure of a signal, may be of help in describing fluctuations of the ionospheric medium. In particular, the technique used here is the ALIF (Adaptive Local Iterative Filter). We have applied ALIF to the characterisation of plasma irregularities in the equatorward boundary of the auroral oval. The data used are from the LEO satellite DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) while it crosses the Equatorward boundary of the oval. The time series analysed are those from the electric field instrument ICE (Instrument de Champ Electrique) on board of DEMETER, and the identification of the equatorward boundary in the time series of in situ data is based on the comparison between the satellite trajectory and the picture of the auroral oval from the simultaneous auroral imaging by the DMSP satellite. In detail, we present an analysis of the multi-scale features and dynamics of ionospheric plasma along the DEMETER trajectory in different regions, which seem to be characterized by plasma irregularities of different nature. A clear change of the multi-scale nature of plasma fluctuations is observed in the correspondence of the irregularities originated by particle precipitation in the equatorward boundary of the auroral oval.