The upper atmosphere and ionosphere of Titan: A coupled model Original Research Article

A coupled model of the upper atmosphere and ionosphere of Titan, which includes all relevant physical processes for neutral and ionized components, is presented for a solar zenith angle of 30°. The main results concerning the ionosphere are: (i) ionospheric peak of about 6 000 electrons per cc appears at 980 km, (ii) the most abundant component near the peak is HCNH+, but at lower altitudes heavy nitrilic and hydrocarbon ions dominate, (iii) termolecular reactions can play an important role in ionospheric chemistry at 700 km and below, only if reaction rates are as large as 5 × 10−23 cm6 s−1.