Wavelet analysis of high‐latitude electric and magnetic fluctuations observed by the Dynamic Explorer 2 satellite

Wavelet analysis has been performed on the low‐frequency (0.1 to 16 Hz) electric and magnetic field variations observed by the low‐altitude polar‐orbiting Dynamic Explorer 2 (DE2) spacecraft. The application of the wavelet transform is conditioned by the fact that both magnetic and electric signals, as well as their ratio, vary along the spacecraft track. They grow from low values in the middle latitudes to the peak values in the center of the auroral zone and then subside in the transition to the polar cap. In such a case the wavelet transform technique appears most adequate for signal processing. Using the wavelet transform of the data, we compute the local intermittency measure and flatness of electric and magnetic fluctuations and demonstrate that both in the auroral zone and in the polar cap they are a manifestation of intermittent turbulence. In order to distinguish between the static and wave interpretations of the turbulent fields, the ratios of magnetic to electric field strengths are computed from wavelet magnitudes. Within the static interpretation, these ratios should be determined by the height‐integrated ionospheric Pedersen conductivity, while in the wave interpretation they should be governed by the inverse impedance of Alfvén waves. It is shown that in the auroral zone, the observed magnetic to electric field ratios are in a better agreement with the values of Pedersen conductance (Σ P ∼ 5–10 mhos). This suggests that the fluctuations predominantly result from spacecraft crossing quasi‐static field structures, which signatures are Doppler shifted when detected in the spacecraft frame.