Correcting radar meteor observations for the initial radius effect

Radar is a useful way to observe the sporadic meteor complex, but it suffers from some biases. The attenuation due to destructive interference within meteor trails of finite width, or initial trail radius effect, is a significant correction factor and is poorly defined. This effect reduces the height to which meteors can be observed with radar and affects observations with higher frequencies more than lower frequencies.; Observations of meteors at three frequencies, 17.45, 29.85 and 38.15 MHz, are used as the basis for a new model of initial trail radius. A model has been constructed which includes fragmentation, the effect of which is more important to the initial radius than the spreading of electrons. The model is shown to explain Geminid observations, and to fit sporadic observations well. The model is used to derive a correction factor for radar meteor fluxes at any wavelength, limiting magnitude and velocity of meteoroid. The correction factor is significantly different from any derived in previous studies. Fluxes of sporadic meteors from five major sporadic sources are calculated for 2000 and 2001 using the new correction factor; significant annual variations are seen in most of the sources indicating differences in the distribution of sporadic radiants around the Earth's orbit.