  Every second millions of small meteoroids enter the Earth's atmosphere
producing dense plasmas. Radars easily detect these plasmas and researchers use
this data to characterize both the meteoroids and the atmosphere. This paper
develops a first-principle kinetic theory describing the behavior of particles,
ablated from a fast-moving meteoroid, that colliside with the atmospheric
molecules. This theory produces analytic expressions describing the spatial
structure and velocity distributions of ions and neutrals near the ablating
meteoroid. This analytical model will serve as a basis for a more accurate
quantitative interpretation of radar measurements and should help calculate
meteoroid and atmosphere parameters from radar head-echo observations.
