Positive-ion composition measurement in the upper mesosphere and lower thermosphere at a high latitude during summer

Abstract

A composite sounding rocket payload was launched from Andoya Rocket Range (69°17′N) on August 8, 1971, 12.11 GMT; it reached a peak altitude of 99.1 km. The main purpose of the launch was to study the ion composition around the cold summer mesopause and its relation to ambient temperature, production, and loss rates. Ions were detected by the mass spectrometer from a height of 70.7 km on the ascent to a height of 69.8 km on the descent, water-cluster ions H+(H2O)n dominating the composition below 84 km. Cluster ions of a higher order of hydration appeared with increasing height until a rapid cutoff occurred in the region from 84.5 to 86.0 km. Simultaneously, metal ions Mg+ and Fe+ appeared, and NO+ and O2+ emerged as dominating species. The largest cluster ion found during ascent was (109 ±1)amu, probably H+(H2O)6, detected in one spectrum at 84.5 km. During descent the largest cluster detected was (91 ±1) amu, probably H+(H2O)5, found in three spectra between 85.9 and 82.2 km. In the cluster-ion region the concentration of O2+ exceeded that of NO+, whereas NO+ exceeded O2+ above the region, the crossover taking place near the water-cluster cutoff.