Impact of a major meteor storm on Earth's ionosphere: A modeling study

A comprehensive model of the effect of a major meteor storm on Earth's iono sphere is presented. The model includes meteor stream mass distributions ba sed on visual magnitude observations, a differential ablation model of majo r meteoric metals, Fe and Mg, and state-of-the-art modeling of the chemistr y and transport of meteoric metal atoms and ions subsequent to deposition. Particular attention is paid to the possibility of direct ionic deposition of metallic species. The model is validated by calculating the effect of an nual meteor showers on the background metal atom and ion abundances. A meta llic ion density increase of up to 1 order of magnitude is observed, in agr eement with in situ measurements during showers. The model is exercised for a hypothetical Leonid meteor storm of the magnitude reported in 1966. The model predicts the formation of a layer of metal ions in the ionospheric E region that reaches peak densities of around 1 x 10(5) cm(-3), correspondin g to a 2 order of magnitude increase of the quiescent nighttime E region de nsity. Although sporadic E layers reaching or exceeding this density are re latively common, the effect is different in that it persists on the order o f days and would be observed over nearly one-half the globe. The model pred ictions are consistent with the available 1966 Leonid storm data. In partic ular, the observation of enhanced, predawn sporadic E activity points to ef ficient collisional ionization of meteoric metals, as assumed in the model.