The quiet auroral ionosphere and its neutral background Original Research Article

Even for quiet conditions the high latitude atmosphere – both neutral and ionised – is inadequately described by general models such as CIRA or MSIS, and IRI, respectively. From the measurements by lidar and falling spheres in northern Scandinavia one can establish neutral pressures which distinctly differ from what CIRA or MSIS predicts. The large number of electron densities available from EISCAT combined with rocket borne probe measurements from Antarctica can be used to construct solar controlled electron densities as a function of solar zenith angle and solar activity. A seasonal variation of these electron densities is implicitly included by establishing electron densities for pressure surfaces of the atmospheric model based on Scandinavian measurements. These “true quiet” high-latitude electron densities are found to be significantly larger than corresponding values from high latitudes just equatorward of the auroral region, which suggests consistently larger NO densities.