On the Necessity of Using <i>foμEs</i> Instead of Foes in Estimating The Intensity and Variability of Sporadic E Layers

Abstract

The ordinary wave critical frequency foEs is measured routinely by ionosondes and used widely in estimating the intensity and occurrence of sporadic E (Es) metal ion layers. Recently, however, it was realized that foEs overestimates Es intensities because it corresponds to the sum of both the layer metal ion plasma and the regular E region plasma densities. To account for this, a new parameter, foμEs , was introduced that corresponds to the Es layer metal plasma density only, and a method was proposed for its calculation. In the present work, an ionosonde data set is analyzed in order to assess the importance of replacing foEs by foμEs in Es studies. To this objective, the diurnal and seasonal variability of sporadic E is re-examined. It turns out that the Es mean diurnal and seasonal variations estimated by means of using foμEs , differ substantially from those based on foEs, implying that the use of foEs leads to biased results and wrong physical inferences. It is therefore urged that foμEs is adopted and used instead of foEs, in future ionosonde sporadic E studies. The same applies for the case of satellite radio occultation (RO) sporadic E investigations as well, where foµEs should be used, instead for foEs, for calibration and validation purposes.