Ar\u3csup\u3e+\u3c/sup\u3e in the Terrestrial Atmosphere

Ar+ in the terrestrial ionosphere is produced by photoionization and electron impact ionization and by the reaction N2+(v \u3e 1) + Ar → Ar+ + N2 (1) The rate coefficient for (1) has been measured by a number of workers and has been found to approach gas kinetic rates. For v=0, the reaction proceeds in the reverse direction. For this reason, the Ar+ densities provide a sensitive measure of the extent of vibrational excitation of N2+ in the terrestrial ionosphere. Model calculations show that at 200 km, half of the source of Ar+ is due to (1). The total density of Ar+ is on the order of 10cm-3 near 200 km