The polarization, frequency, and wavelengths of high‐latitude turbulence

A new feature of electric field frequency‐time spectrograms observed on the S3‐3 satellite, the resonance fingerprint, is used to determine the polarization, frequency, and wavelengths of high‐latitude turbulence. It is found that in the rest frame of the plasma the frequency is approximately zero, the wavelength may be as small as 5 m, and the electric field is polarized in the plane normal to the magnetic field. Consequently, the power spectrum below a few hundred hertz as measured by a satellite is dominated by the Doppler shift of zero frequency turbulence. The resonance fingerprint is a characteristic pattern of bite‐outs in the electric field power spectrum which repeats at twice the spin frequency of the satellite. The bite‐out, an interference effect, is a consequence of the fact that a double probe is insensitive to wavelengths such that the double‐probe separation is an integral multiple of wavelength.