Context. The Cassini probe regularly passes in thevicinity of Titan, revealing new insights into particle precipitationthanks to the electron and proton spectrometer. Moreover, the Huygensprobe has revealed an ionized layer at 65km induced by cosmicrays. The impact of these different particles on the chemistry of Titanis probably very strong. Aims. In this article, we compute the wholeionization in the atmosphere of Titan: from the cosmic rays near theground to the EUV in the upper atmosphere. The meteoritic layer is nottaken into account. Methods. We used the transTitan model to compute theelectron and EUV impact, and the planetocosmics code to compute theinfluence of protons and oxygen ions. We coupled the two models tostudy the influence of the secondary electrons obtained byplanetocosmics through the transTitan code. The resulting modelimproves the accuracy of the calculation through the transport ofelectrons in the atmosphere. Results. The whole ionization is computed andstudied in details. During the day, the cosmic ray ionization peak isas strong as the UV-EUV one. Electrons and protons are very importantdepending the precipitation conditions. Protons can create a layer at500km, while electrons tend to ionize near 800km.The oxygen ion impact is near 900km. The results shows fewdifferences to precedent models for the nightside T5 fly-by of Cassini,and can highlight the sources of the different ion layers detected byradio measurements. Conclusions. The new model successfully computes theion production in the atmosphere of Titan. For the first time, a fullelectron and ion profile has been computed from 0 to 1600km,which compares qualitatively with measurements. This result can be usedby chemical models. Key words: planets and satellites:individual: Titan - atmospheric effects - Sun: UV radiation - spacevehicles: instruments - methods: numerical
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