meteor trail[′mēd·ē·ər ‚trāl]
the train remaining in the atmosphere after the passage of a meteor. There are two types of meteor trails: dust trails and gas, or ionized, trails. Dust trails are formed only by bright bolides at heights of 25–80 km as a result of the condensation of vapors of meteoric material in the head and train of the bolide and the solidification of droplets of molten material blown off the meteor’s surface. At twilight, the luminosity of dust trails is the result of the scattering of sunlight by minute particles, measuring less than 10 ~4 cm in diameter. Dust trails are visible for periods of up to several hours. The luminosity of ionized trails results from recombination processes; the spectra of these trails show lines of Mg, Na, Ca, Fe, and other elements. Ionized trails are formed by all meteors, but only those of bright meteors can be observed by the naked eye. They are visible for periods ranging from fractions of a second to several minutes. Because radio waves are reflected by ionized trails, such trails can be observed by radar.
Initially, the meteor trail is straight and thin; however, wind and diffusion soon cause it to curve and broaden. Optical and radar observations of meteor trails are one of the principal methods of studying the circulation and turbulence of the earth’s atmosphere at heights of 80–110 km.
V. N. LEBEDINETS