Altitudinal dependence of meteor radio afterglows measured via optical   counterparts
  Utilizing the all-sky imaging capabilities of the LWA1 radio telescope along with a host of all-sky optical cameras, we have now observed 44 optical meteor counterparts to radio afterglows. Combining these observations we have determined the geographic positions of all 44 afterglows. Comparing the number of radio detections as a function of altitude above sea level to the number of expected bright meteors we find a strong altitudinal dependence characterized by a cutoff below $\sim$ 90 km, below which no radio emission occurs, despite the fact that many of the observed optical meteors penetrated well below this altitude. This cutoff suggests that wave damping from electron collisions is an important factor for the evolution of radio afterglows, which agrees with the hypothesis that the emission is the result of electron plasma wave emission. 
K. S. Obenberger, J. M. Holmes, J.D. Dowell, F. K. Schinzel, K.   Stovall, E. K. Sutton, and G. B. Taylor
astro-ph.EP astro-ph.IM physics.space-ph