The confusion which has existed for decades about the relationship between temperate zone sporadic E, as seen on an ionosonde, and meteor incidence has been resolved by identifying three classes of meteor-produced Es (herein called Em)) Class 1 Em is the instantaneous partially reflecting ionosonde echo due to a single meteor trail. Correspondence in height and time of single echoes has long been established, but no statistical work relating these echoes directly to meteor occurrence rates has yet been done. Class 2 Em defines the cases where meteor occurrence is of sufficient strength to produce control of fEs on the simultaneous ionogram. This is a rare occurrence and has accounted for much of the ambiguity in the literature where direct relationships have been sought between meteor rate and Es occurrence from tabulated ionosonde data. Class 3 Em is the production of Es layers by the subsequent action of wind shear on residual meteor ion concentrations. This is identified statistically by the probability of occurrence of Es above at least 4 MHz or preferably above somewhat higher frequencies. A major conclusion which emerges is that much temperate zone Es, but not necessarily all, is of this type.
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