Large airglow enhancements produced via wave-plasma interactions in sporadic E

• Published in: Geophysical research letters 1999-06, Vol.26 (11), p.1557-1560
• Main Authors: Djuth, F. T., Bernhardt, P. A., Tepley, C. A., Gardner, J. A., Kelley, M. C., Broadfoot, A. L., Kagan, L. M., Sulzer, M. P., Elder, J. H., Selcher, C., Isham, B., Brown, C., Carlson, H. C.
• Format: Article
• Language: English
• Subjects: Earth, ocean, space; Exact sciences and technology; External geophysics; Interactions between waves and particles; Physics of the ionosphere
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/1999GL900296

In the past there has been great interest in monitoring enhanced 557.7 nm O(¹S) emissions from the thermosphere in connection with high‐power, high‐frequency (HF) radio wave modification of the F region ionosphere. These emissions are considered to be evidence that the HF‐modified electron distribution function is non‐Maxwellian because a significant flux of ∼5–6 eV electrons is required to produce the airglow. The suprathermal tail is believed to develop as a result of nonlinear plasma processes. Past F region observations of 557.7 nm airglow at Arecibo Observatory, Puerto Rico have yielded only a few Rayleighs of enhanced emissions. Recently, airglow enhancements were monitored in sporadic E above Arecibo. Surprisingly, these experiments yielded ∼55 Rayleighs of enhanced 557.7 nm airglow and the first observations of emissions from the N2 first positive molecular bands. The observations imply that a large flux of energetic (5–10 eV) electrons is generated as part of the wave‐plasma interaction in sporadic E.