Titan's upper ionosphere

Abstract

As a result of electron impact ionization and photoionization, an ionosphere should be built up at the high-altitude region of Titan's atmosphere. New calculations presented here predict the presence of significant amounts of CH5(+), N2H(+), C2H2(+), and C2H3(+) ions near the ionospheric peak. Because of fast ion-neutral reactions with CH4 and N2, the number density of the Ar(+) ions would not exceed a value of more than 10/cu cm in the upper ionosphere if argon has a mixing ratio about 0.01 near the homopause. The ionospheric flow dynamics are studied in the limits of one-fluid mass-loaded flow and of diffusion-convection approximation. Both approaches show that ion-neutral friction acts as a cushion against plasma streaming effects.