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 meteorproduced Es (herein called Era). 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 res 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 M Hz 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.
Soc. London, 51, 81, 1939. Axford, W. I., Note on a mechanism for the vertical transport of ionization in the ionosphere, Can. d. Phys., 39, 1393, 1961. Axford, W. I., and D. M. Cunnold, Wind-shear theory of temperate zone Es, Radio Sci., 1, 191, 1966. Bhar, J. N., The effect of meteoric shower on the ionization of the upper atmosphere, Nature, 139, 470, 1937a. Bhar, J. N., Meteors and upper atmosphere ionization, Indian J. Phys., 11, 109, 1937b. Briggs, B. H., Investigation of certain properties of the ionosphere, Proc. Phys. Soc. London, Sect. B, 64, 267, 1951. Chatterjee, B., Nature and origin of sporadic E regions as observed at different hours, J. ,4tmos. Terr. Phys., 3, 229, 1953. Chimonas, G., Wind-driven instability in the lower E region, J. Geophys. R es., 74, 4091, 1969. Chimonas, G., Enhancement of sporadic E by horizontal transport within the layer, J. Geophys. Res., 76, 4578, 1971. Chimonas, G., Wind component exchange and the rapid vertical movement of a sporadic E layer, J. Geophys. Res., 78, 5636, 1973. Chimonas, G., and W. I. Axford, Vertical movement of temperatezone sporadic E layers, J. Geophys. Res., 73, 111, 1968. Cuchet, L., Role of a complex ionic composition in the wind shear theory of sporadic E, Radio Sci., 1, 1101, 1966. Cuchet, L., The role of meteoric ionization in the phenomenon of sporadic E layer, C. R. Acad. Sci., Ser. B, 264, 952, 1967. Doniy, V. N., Role of meteors in Es formation, Geomagn. A eron., 11, 915, 1971. 6134 ELLYETT AND GOLDSBROUGH: METEORS AND SPORADIC E, 1 Eckersley, T. L., Irregular ionic clouds in the E layer of the ionosphere, Nature, 140, 846, 1937. Ellyett, C., Solar influence on meteor rates and on atmospheric density variations at meteor heights, submitted to J. Geophys. Res., 1976. Fiocco, G., Optical radar results and ionospheric sporadic E, J. Geophys....
