Ionospheric processes associated with intense subauroral electric fields

Observations of ionospheric parameters were made near an equatorward edge of the auroral oval. Using both experimental data and theory, the ionospheric response to substorm related intense localized electric fields at subauroral latitudes is discussed. A deep depletion in the ionospheric electron density was found to be colocated with these large electric fields at magnetic latitudes as low as 53 deg. It is shown that the associated field aligned currents are very weak in this region and that it is the F region structure which dominates the conductivity gradient rather than the E region. The experimental data also indicate that the trough develops much more quickly than present theories predict, at least near the F peak. It is also shown that when a sheared or turbulent velocity field is present within a scattering volume, the scatter radar spectra will be distorted. Two different cases (large scale velocity shear and small scale turbulent velocity fluctuations) are studied and the theory is compared with observed distorted spectra obtained in scattering volumes known from in situ data to contain perpendicular velocity fluctuations. Results are discussed