Modeling and observing the effect of aerosols on meteor radar measurements of the atmosphere

Measurements of the time taken for meteor radar echoes to decay can be used to estimate the ambipolar diffusion coefficient. If it is assumed that the decay of the radar echo is due strictly to the outward diffusion of ionized material in the meteor's trail, then echo decay is determined by temperature and pressure. However, dust particles or small ice crystals may absorb electrons from meteor trails, distorting their evolution and echo decay properties. A numerical method for modeling these processes is presented, with the prediction that absorbing aerosols can both decrease and increase the decay time of meteor radar echoes, depending on meteor, atmospheric, and radar parameters. This prediction is confirmed with observations taken using three 33 MHz and two 55 MHz radars at three locations in Australia and Antarctica, which display strong biases in the decay times of lower power echoes. It is suggested that both the accuracy and precision of atmospheric measurements are improved if only the highest power meteor echoes are used for estimates of the ambipolar diffusion coefficient.