Further studies of the Perkins stability during Space Weather Month

A simple integral equation describing the height of the mid-latitude ionosphere is presented and compared with observations and a more sophisticated model. At any instant, the ionosphere moves toward an equilibrium altitude, if it exists, which is determined by a combination of southward wind and eastward electric field. If no equilibrium exists, the layer simply falls at its terminal velocity or at a wind or electric field-aided rate. Including a simple recombination model provides an even more complete characterization of the nighttime ionosphere. By comparing the measured and predicted content, an estimate of the flux from the plasmasphere is possible. (C) 2003 Elsevier Ltd. All rights reserved.