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.