Metallic ions in the equatorial ionosphere

Journal of Geophysical Research Atmospheres (Impact Factor: 3.43). 03/1973; 78(4). DOI: 10.1029/JA078i004p00734
Source: NTRS


Four positive ion composition measurements of the equatorial E region at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO+ and O2+. The relative concentrations are similar to those observed at midlatitudes but exhibit unusual structural behavior with altitude. A metallic ion layer centered at 92 km is found to contain Mg+, Fe+, Ca+, K+, Al+, Na+, and possibly Si+ ions. The layer is explained in terms of a similarly shaped altitude distribution of neutral atoms that are photoionized and charge exchanged with NO+ and O2+. Three-body reactions form molecular metallic ions that are rapidly lost by dissociative ion-electron recombination.

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Available from: A. C. Aikin, Mar 25, 2014
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    • "Each of these techniques have unique capabilities. [3] Ion mass spectrometers carried on sounding rockets and satellites have been useful in identifying all of the metal species associated with meteoric ablation [e.g., Johnson and Meadows, 1955; Istomin and Pokhunkov, 1963; Narcisi and Bailey, 1965; Narcisi, 1968; Aikin and Goldberg, 1973; Grebowsky and Aikin, 2002] . Although the rocket measurements provide precise altitude profiles of multiple metal species, they usually only measure ionized species. "
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    ABSTRACT: UV radiances from the Global Ozone Monitoring Experiment (GOME) spectrometer on the ERS-2 satellite are used to determine long-term dayside temporal variations of the total vertical column density below 795 km of the meteoric metal species Mg and Mg+ in the upper atmosphere. The GOME instrument has the ability to observe the ground state transition lines of Mg I at 285.2 nm and resolve the Mg II at 280 nm. A retrieval algorithm has been developed to determine column densities and applied to the years 1996–1997. Results show the middle latitude dayside Mg+ peaks in total vertical content during the summer, while neutral Mg demonstrates a much more subtle maximum in summer. Dayside trends are opposite previous midlatitude nighttime lidar observations, with the exception of calcium. The Mg+/Mg ratio has a seasonal variation, reaching a maximum in the summer. The total content of Mg+ is twice that of neutral Mg.
    Full-text · Article · Mar 2008 · Geophysical Research Letters
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    • "A great deal of this incoming meteoric material is ablated in the 70 to 150 km altitude region. The resulting metal ions and neutrals are deposited in the mesosphere and lower thermosphere as first detected by ground-based sodium observations (Slipher, 1929, Cabannes and Duffy, 1938 ) and rocketborne ion mass spectrometer measurements (Johnson and Meadows, 1955; Istomin and Pokhunkov, 1963; Narcisi and Bailey, 1965; Narcisi, 1968; Aikin and Goldberg, 1973). Lidar observations have added seasonal metal measurements at fixed locations ( Gerding et al, 2000; Raizada and Tepley, 2003). "

    Full-text · Article · Sep 2006
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    • "Of a total of 11 experiments for which Na+ concentrations have been reported (Aikin and Goldberg , 1973; Alpers et al., 1993; Kopp and Hermann, 1984; Kopp, 1997), 2 showed concentrations around lo4 crnmS (Alpers et al, 1993; Kopp, 1997) and the rest gave values between 30 and 1000 cmw3. It may be significant that the early measurements (Aikin and Goldberg, 1973) all showed sodium ion concentrations of less than 100 cm-', whereas the later studies (Alpers et al., 1993; Kopp and Hermann, 1984; Kopp, 1997) showed values greater than 100 cm-'. It could be that the measuring techniques used in the early measurements were inadequate for measuring such low ion concentrations. "
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    ABSTRACT: Sporadic layers of metal atoms (Ns), occurring in the same height range as ionospheric sporadic-E layers, were first detected by lidar some 20 years ago. Ns layers have typical thicknesses of a few hundred meters to a few km, peak atom concentrations several times that of the ambient background layer, and are sometimes seen to grow and decay over time scales as short as a few minutes. Layers have been detected in Na, Fe, K and Ca, but it seems likely that they exist in other meteoric metals such as Mg. Despite a great deal of excellent experimental work over the past decade, the source of Ns layers is still an open question. Mechanisms suggested include direct meteor deposition, release from aerosol particles, chemical reduction of appropriate metal compounds, redistribution of existing atoms, and recombination of ions. The last-named of these mechanisms, although capable of explaining many of the observed characteristics of Ns layers, including their strong correlation with Es, has generally been rejected in the past, at least in the case of Na, because mass spectrometer measurements of Na+ have mostly shown concentrations too small to explain the observed sporadic sodium layers. However, recent laboratory measurements of the relevant recombination processes, and a re-evaluation of the rocket-borne mass-spectrometer measurements, suggest that ion recombination is in fact the strongest contender.
    Full-text · Article · Jan 1999 · Advances in Space Research
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