A theory of long-duration meteor-echoes based on atmospheric turbulence with experimental confirmation

A theory of long-duration meteor-echoes is developed, based on the assumption that a meteor-trail is rendered rough by the action of the small eddies in the atmosphere. This theory leads to the conclusion that, if loss of electrons from the trail by recombination and/or attachment is neglected, the field-strength of a long-duration meteor-echo in its decay-phase should be inversely proportional to the cube of time subsequent to formation of the trail. It is shown that this law is verified experimentally in the early part of the decay but that at later times the decay becomes more rapid. This can be explained in terms of the loss of electrons from the trail, provided that the loss is due to attachment to atmospheric molecules and the attachment time has an average value of the order of seven seconds. It is shown that the spectrum of incoherent scattering associated with turbulent mixing in a gradient of electron-density may be derived experimentally by measuring the frequency-dependence of long-duration meteor-echoes during their decay-phase. This measurement is carried out, and the results are related to the CRPL experiments concerning the frequency-dependence of long-distance VHF scatter-transmission (see Fig. 12). It is deduced that the contribution of meteoric ionization to the background-signal of scatter-transmission arises mainly from the incoherent scattering associated with mixing of this ionization by atmospheric turbulence. According to our analysis, McKinley's data concerning the contribution of meteor-trails to scatter-transmission lead to the same conclusion.