M. Light, S. Close, P. Colestock and J. Zinn

*Los Alamos National Laboratory, Los Alamos, NM, USA*

One of the most important aspects of meteor physics that remains to be determined in detail is the distribution of meteor mass and flux, especially for the observed large population of sub-microgram meteors. As these meteors are burned up by entering the atmosphere, they create a plasma which can register a measurable return in large-aperture radar. Although an extensive body of large-aperture radar scattering data from these meteor head plasmas has been accumulated in recent years, the essential physics that relates the measured radar cross-section to meteor mass and velocity has only been partially formulated in the limit of long-wavelength scattering from nominally spherical plasmas. In this work we extend that treatment to include fully electromagnetic scattering from inhomogeneous meteor head plasmas, whose expected density profiles are determined from first-principle fluid or Monte-Carlo simulations. The results indicate that the plasma parameters vary widely with altitude, as expected, and hence with the initial meteor mass. Moreover, we develop a general model for the scattering based on both an exact calculation via the method of moments and the geometrical theory of diffraction which can be used with the markedly non-spherical meteor head plasmas that can occur in some experimentally relevant regions of parameter space. The implications of this scattering model for the interpretation of large-aperture radar scattering data will be described.