Relationship of meteors to sporadicE, 1. A sorting of facts

Abstract

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....

Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

“…Appleton and Naismith (1947) reported longer-duration sporadic-E during periods of shower activity. Ellyet and Goldsborough (1976) and Whitehead (1970) have summarized the results on the contribution of metallic ions in the formation of sporadic-E. Ellyet and Goldsborough (1976) have further studied the relationship of meteors to sporadic-E and identified three classes of meteor produced sporadic-E, termed as E m . Class 1 of E m is the instantaneous partially reflecting echo due to a single meteor trail, which has lifetime of minutes at ionosonde frequencies.…”

Changes in the Frequency Distribution Characteristics of Ionosonde Es Parameters During Major Meteor Activity

“…1 shows the seasonal variation of radar meteor activity recorded at Christchurch (geographic 172°.5, -43°.5) employing a 69 MHz mono static system with an omnidirectional antenna system sensitive to diverse meteor radiants on the celestial hemisphere. The hourly rates are composed using 3t years data between 1960 and 1965 (Ellyett and Keay 1961;Keay and Ellyett 1969) and are the mean values between 00 and 12 LMT when the major diurnal influx occurs. Radar surveys achieve a greater statistical significance than is possible with less sensitive visual observations, and Fig.…”

“…Although the meteoric source of temperate latitude Es has long been recognized and although meteor ions have been identified during meteor showers (Goldberg and Aikin 1973), the expected close association between meteor influx and Es recorded on ionograms has been difficult to establish. It is clear that the complex aeronomy governing Es production can lead observationally to a rather indirect relationship between the two phenomena.…”

“…The majority of temperate latitude Es events are produced by the redistribution of the reservoir of lower thermosphere meteoric ions by the action of wind shears in the presence of the geomagnetic field producing ionization irregularities. Ellyett and Goldsbrough (1976) employed the terms 2Em and 3E m for the classes of immediate and delayed sporadic-E. The present paper is concerned with the latter events.…”

“…Seasonal variation of radar meteors obtained at Christchurch (geographic 172°.5, -43°.5) obtained from the 3!-years data of Ellyett and Keay (1961) and Keay and Ellyett (1969). The ordinate is the mean hourly rate between 00 and 12 LMT over 5 day intervals.…”