A Study of Sporadic E Layer Chemistry
Abstract
Sporadic E layers in the lower thermosphere play a very important role in radio communications. The lifetimes of these transient layers are largely controlled by the ion-molecule chemistry of metallic ions, particularly iron (Fe), that are produced by meteoric ablation. The aim of this project was to study the role of atomic oxygen in controlling the rate at which Fe(+) ions are neutralised. The rate coefficients for the reactions of Fe(+) with N2O, O2 and N2, and the reactions of FeO(+) with CO and O, were measured using a fast flow tube coupled to a mass spectrometer, with Fe(+) ions produced by the pulsed laser ablation of an iron rod. Very good agreement was achieved with previous measurements of the first four reactions. The reaction of FeO(+) and O was found to be about 100 times slower than the Langevin limit. The results were then employed in a mesospheric model, which is now able to predict the top-side scale height of the atomic Fe layer and the ratio of Fe(+)/FeO(+) above 90 km in good accord with observations. Finally, a combination of emission spectroscopy and ab initio quantum theory was used to show that FeO(+) does not have an excited electronic state that would provide a suitable LIDAR probe in the atmospheric transmission window.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2002
- Accession Number
- ADA406401
Entities
People
- John M. Plane
Organizations
- University of East Anglia