Determination of the sources and sinks of N + ions in the thermosphere

Measurements of atmospheric parameters made by the Atmosphere Explorer‐C satellite are used to identify mechanisms for the production and loss of N + ions in the ionosphere. The main source below 250 km is found to be photo‐dissociative ionization of N 2 . Above 250 km the reactionO +( 4 S ) + N ( 2 D )→ k 1N +( 3 P ) + O ( 3 P )is dominant; k 1 is found to be 5 −2 +7 × 10 −11 cm³s −1 . A possible minor source of N + is the reactionO +( 2 P ) + N 2→ k 2N + N Owhere k 2 = 1 −.5 +1 × 10 −10 cm³s −1 . Photoionization of N( 4 S) and dissociative charge exchange of He + with N 2 constitute detectable sources above 350 km. Charge exchange of N + with O is identified as a significant sink above 300 km. The rate coefficient for this reaction is 5 −2 +7 × 10 −13 cm³s −1