Ionospheric layer induced by meteoric ionization in Titan's atmosphere

The ablation of meteoroids and the ionization of metallic ions in the atmos phere of Titan has been investigated. The ionization rates of the most abun dant metals in cometary meteoroids, Si+,Mg+ and Fe+, are calculated From th e meteoroid mass loss rate and the ionization probability of each metal. We have modeled the ion-neutral chemistry of metallic ions and calculated the concentration of the most abundant metal ions and electrons. We found that long-lived metallic ions considerably change the predictions of the electr on density by the models which only consider solar radiation and electrons trapped in the magnetosphere of Saturn. The inclusion of metallic ions in t he upper ionospheric models leads to an increase in the electron concentrat ion below 800 km. We conclude that an ionospheric layer should be present a t around 700 km with an electron density peak similar in magnitude to the o ne produced by solar radiation at 1000 km or by cosmic rays at 90 km. (C) 2 001 Elsevier Science Ltd. All rights reserved.