The ionizing effects of meteors

It is shown that a meteor of average velocity has enough energy to cause ionization of atmospheric gases by impact. Recent experimental work by Frische and others on collisions of ions is interpreted as supporting the hypothesis that meteoric collisions do result in ionization. The afterglow of nitrogen is considered as a possible example of the process by which a meteor train remains glowing for a period of minutes and the coincidence of the region in which such trains are generally observed and of the E region of the upper atmosphere is pointed out. The spectra of bright meteors, while not showing atmospheric lines, are shown not to be inconsistent with the above hypothesis. The behavior of the transatlantic short-wave radio telephone circuits of the American Telephone and Telegraph Company, during 1930, 1931, and 1932, is examined for possible meteoric effects. It is concluded that, in general, a rather large shower is necessary to affect them appreciably. This was to be expected since these circuits are normally under a continuous bombardment by random meteors. It seems possible that a certain degree of the variability (rapid fading, etc.) of received signals over such paths is due to this bombardment. Results of radio pulse studies of the upper atmosphere, particularly by Schafer and Goodall, which are strongly suggestive of meteoric ionization, especially at times of special meteoric activity, are (1) sudden increases in ionizaton in the E region lasting for a period of minutes or less, and (2) increases of longer duration with maxima coincident in time with those of observed meteoric activity. Such tests made during the Leonid shower of November, 1932, were successful in correlating sudden increases in ionization in the E region with the visual observations of a number of bright meteors passing overhead. For the brightest meteor observed, the ionization increased to a value in excess of summer noon conditions. It is pointed out that meteoric showers might take place in the F region which would be unobservable by ordinary visual means. Taking into account the energy spent by the meteor in ionization, a mass for the brightest meteor, for which correlative data was obtained is roughly calculated to be 0.3 gram. Its estimated brightness was −1 magnitude. The recombination coefficient at the height of the E region is calculated from the rate of decrease of ionization after the passage of a meteor, to be less than 0.2 × 10
⁻⁸
cubic centimeters per second.