The effect of attachment on radio echo observations of meteors

Abstract

This paper is concerned with the effects of electron attachment to neutral air molecules on the characteristics of radio echoes from meteor trails. Previously it has been assumed that diffusion processes were primarily responsible for the reduction of volume electron density in a meteor trail, and also in limiting the echo duration. In a companion paper a value of the attachment coefficient β e = 5 x 10 -15 cm 3 s -1 has been determined from combined photo­graphic and radio echo observations of a meteor. An effect of an attachment coefficient of this magnitude is to reduce the expected echo duration by a factor of 1000 or more for a bright fireball. The observed relation between visual meteor magnitude and echo duration is explained by this mechanism, as are the departures from the wavelength squared variation of echo dura­tion predicted by diffusion theory. Attachment processes also account for the observation that the final heights of enduring meteor echoes all centre about 95 km, even though bright meteors may show a maximum in light intensity below 80 km.