The small-scale structure of the high-latitude topside ionosphere is investigated through electric-field and electron-density measurements made by the Arcad-Aureol-3 satellite. The frequency range is between 12.5 and 200 Hz, which, under the hypothesis of zero frequency turbulence, corresponds to spatial wavelengths between 40 and 640 m. Two different groups of regions are identified, in which different types of turbulence are observed: the arc region of the auroral zone, where intense sporadic turbulence events occur, which are associated with precipitations, parallel current, and velocity shears; and the polar cap, diffuse auroral zone and subauroral region, where the turbulence is less intense and often associated with density gradients. The frequency spectra of the electric and density fluctuations generally have a power law shape. The distribution of the spectral indices is different in each type of turbulence, with smaller and less dispersed values in the E x B turbulence than in shear-associated turbulence.