Data from the Midcourse Space Experiment Tilere is evidence (R. H. Picard, J,'unes H. Brown (MSX) has provided the first observations of thunderstorm-personal communications, 1997) that gravity wave generated gravity waves imaged from space. Gravity wave structures are present in a number of MSX MWIR images. theory predicts that isolated, sufficiently convective This evidence is based on morphology, length scales, thunderstorms can launch waves mid create a unique power specUa and MWIR mdimive properties. The present intensity pattern of concentric circles on a radiating sinface paper shows that in particular cases the sources of these of constant altitude above such a storm. banong the MSX waves can be established as thunderstorms. This source constant-nadir-angle mid-wave hlfmred (MWIR) identification was prompted by the work of Taylor anti observations, two instances of such patterns have been Hapgood [1988] who showed that a pattern of concentric identified. It was conf'mned frown •neteorological satellite circles in ground-based observations of nightglow images that highly convective isolated thunderstorms emissions in the mesopause region was caused by va• occurred at the locations and ti•nes expected. isolated thunderstorm that occurred six hours prior to the nightglow observation.

The spectral characteristics and fluorescent efficiencies for electron excitation of nitrogen and air at 600 Torr have been determined. Results are presented for the efficiency of conversion of electron energy to optical radiation in approximately one hundred resolved spectral components of air and nitrogen between 3200 and 10 800 Å when bombarded by 50-keV electrons. The total fluorescent efficiency under these conditions is (0.14±0.02)% for nitrogen and (6.7±1.0)×10—3% for air. In nitrogen the first positive (B 3Πg→A 3Σu+), second positive (C 3Πu→B 3Πg), Gaydon green, Herman infrared, and Goldstein—Kaplan (C′ 3Πu→B 3Πg) band systems of N2 and the first negative (B 2Σu+→X 2Σg+) band system of N2+ were observed. The (0–2) and (0–3) transitions of the Herman infrared system and [N I]32(2D—2P) forbidden doublet at 1.04 μ, previously unreported in the laboratory, were observed. In air the first positive and second positive band systems of N2 and the first negative band system of N2+ were observed as well as atomic spectra of nitrogen, oxygen, and argon.

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Abstract.Distinctive structure in the 4.3-/•m spectral region has been imaged by the SPIRIT 3 radiometer on the MSX satellite observing the cloud-free atmosphere. We show nadir, high-nadir-angle (NA) sublimb, and limb images which, coupled with radiative transfer analysis, indicate that this structure originates from internal gravity waves (GWs). Such structure occurs in a significant fraction of both below-the-horizon (BTH), or sublimb, and above-the-horizon (ATH), or limb, obser-

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