Some ionospheric Sporadic-E studies

Abstract

Ionospheric data relating to the height and incidence of Sporadic-E (E ) has been considered for a number of stations, the normal parameter used being the percentage incidence of greater than a certain specified frequency. Variations in this incidence have been studied on a diurnal and seasonal basis, with respect to magnetic activity, and for different levels of solar activity as represented by the IGY (1957/58) and IqsY (1964/65) periods. The behaviour of E in the auroral region has been examined in detail both in relation to occurrences of all types of E and those types which occur specifically at high latitudes. An E auroral zone has been defined and its properties determined in relation to diurnal, seasonal, solar cycle and magnetic activity changes. The behaviour of the critical frequency and equivalent height of E layers has been interpreted in terms of a two zone model containing a diffuse and a discrete zone. The properties of the two zones and of the E layers are related to the energy of the precipitated electrons. Rocket and satellite measurements of electron energy spectra have been used to calculate electron density profiles as a function of latitude and reflection heights compared with those based on ground based observations. Reasonable agreement is obtained between the two sets of measurements. The Phillips Rule relating to the cumulative distribution of E has been found to apply to all the stations considered at a frequency above the most probable frequency possible interpretations have been given for the gradient of the straight line obtained with the distribution and this gradient is found to show a dependence on latitude which is similar for quiet and disturbed magnetic conditions. This study has also been made of different types of E and their relationship to magnetic activity. Evidence is given to suggest that the changes in the incidences of low type E may be related to changes in the magnetic field. Changes in the behaviour of cusp-type E are considered to be related to the interaction of the quiet solar and disturbed polar current systems. It has also been found that the superposition of low and high type E has a magnetic dependence which is very similar to that of flat type.