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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    • "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.
    Advances in Space Research 01/1999; 24(5-24):547-556. DOI:10.1016/S0273-1177(99)00199-4 · 1.36 Impact Factor
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    • "The development of the Lidar technique later allowed for detailed probing of the atmospheric sodium layer and variations therein with the seasonal and yearly cycles [e.g., Megie and Blamont, 1977]. Later, rocket-born mass spectrometry [e.g., Kopp and Herrman, 1984; Aikin and Goldberg, 1973] began to reveal the details of the mesospheric metal ions as well. With the advent of satellite photometry, information on the structure and dynamics of thermospheric metals also became available [e.g. "
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    ABSTRACT: Metals in the Earth's atmosphere are of interest and importance for several reasons. Emission lines from the sodium layer are used for wave front corrections in imaging space objects. The ionospheric metals present background contamination for remote sensing and tracking of space- born objects. Ionization during meteor showers may also interfere with communications. Although it is generally accepted that extraterrestrial material is the source of metals in the atmospheric, the relative abundances of mesospheric metals and ions present us with a conundrum. Lidar observations have consistently shown that the abundances of neutral metals in the atmospheric and the abundances of these metals in the meteoric material that falls to earth are significantly disproportionate. For example, the column density of neutral sodium is perhaps two orders of magnitude larger than that of calcium, while the abundances in meteorites are approximately equal. To complicate matters further, ion mass spectroscopy has shown that the abundances of the meteoric ions match reasonably well those in the meteorites. We present here a model that attempts to address these discrepancies. At the heart of the model is the concept of differential ablation, which suggests that more volatile metals sublimate earlier in the descent of a cosmic dust particle than do the less volatile components. The modeling is carried out comprehensively, beginning with the heating and vaporization of the dust particles. The vaporization rate is computed as a function of altitude from an ensemble of particles to give a deposition function which is then injected into a fully time-dependent kinetic code which allows for vertical diffusion and includes diurnal dependence through both the models of the major atmospheric components and through transport of the ions due to electric fields.
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    • "However, t h e t o t a l content remains fixed i n :he presence of t h i s d r i f t . A detailed discussion of t h i s proLler,, can be found i n Aikin and Goldberg (1973). Above 200 km on both f l i g h t s , t h e l i g h t metallic ions 23+, 2 4 ' and 2 8 ' are observed i n concentratiom of lo/&. "
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    ABSTRACT: The first in situ measurements of ion composition in the nighttime equatorial E- and F-region ionospheres are presented and discussed. These profiles were obtained by two rocket-borne ion mass spectrometers launched from Thumba, India, on March 9-10, 1970. Ionosonde data established that the composition was measured at times bounding a period of F-region downward drift. During this period, the ions O(+) and N(+) were enhanced by 1-3 orders of magnitude between 220 and 300 km. Below the drift region, O(+) ceased to be the major ionic constituent, but the concentrations of O(+) and N(+) remained larger than predicted from known radiation sources and loss processes. Here also, both the O2(+) and the NO(+) profiles retained nearly the same shape and magnitude throughout the night in agreement with theories assuming scattered UV radiation to be the maintaining source.
    07/1974; 79(16). DOI:10.1029/JA079i016p02473
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