Ar(+) in the terrestrial ionosphere

The Ar(+) densities in the terrestrial ionosphere are computed for both low and high solar activity models. The reaction N2(+)(v greater than 0) + Ar yields N2 + Ar(+) is found to be a significant source of Ar(+) nearly equal to photoionization and electron impact ionization in the high solar activity model. Peak densities of Ar(+) of 11 per cu cm near 190 km and 22 per cu cm near 220 km are predicted for the low and high solar activity models. It is suggested that a simultaneous measurement of Ar(+) and Ar densities would provide a test for the presence of vibrationally excited N2(+) in the terrestrial ionosphere.