An ion‐molecule mechanism for the formation of neutral sporadic Na layers

Cox, Rachel M.; Plane, J. M. C.

doi:10.1029/97jd03376

Cited by 152 publications

(172 citation statements)

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“…Furthermore, the recombination rate of molecular ions increases with decreasing altitude and the chemical equilibrium between ions and atoms tends towards a larger share of atoms with decreasing altitude. Similarly, the chemistry-based model studies of Cox and Plane (1998) for the formation of sporadic Na layers confirm the role of dissociative recombination of molecular ions for forming Na atoms. The delayed conversion of Ca + ions into Ca atoms leads us to expect that the lidar will be able to detect simultaneous neutral Ca s layers at the altitudes of only those Ca + s layers which were either strong or long-lasting (see Fig.…”

Section: Interpretation Of Variations and Implications For The Formatmentioning

confidence: 81%

Sporadic Ca and Ca<sup>+</sup> layers at mid-latitudes: Simultaneous observations and implications for their formation

et al. 2001

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Abstract. We report on the observations of 188 sporadic layers of either Ca atoms and/or Ca ions that we have observed during 112 nights of lidar soundings of Ca, and 58 nights of Ca + soundings, at Kühlungsborn, Germany (54 • N, 12 • E). The Ca + soundings have been performed simultaneously and in a common volume with the Ca soundings by two separate lidars. Correlations between sporadic neutral and ionized metal layers are demonstrated through four case studies. A systematic study of the variations of occurrence of sporadic Ca and Ca + layers reveals that neutral and ionized Ca layers are not as closely correlated as expected earlier: (a) The altitude distribution shows the simultaneous occurrence of both sporadic Ca and Ca + layers to be most likely only in the narrow altitude range between 90 and 95 km. Above that region, in the lower thermosphere, the sporadic ion layers are much more frequent than atom layers. Below 90 km only very few sporadic layers have been observed; (b) The seasonal variation of sporadic Ca layers exhibits a minimum of occurrence in summer, while sporadic Ca + layers do not show a significant seasonal variation (only the dense Ca + layers appear to have a maximum in summer). At midlatitudes sporadic Ca layers are more frequent than sporadic layers of other atmospheric metals like Na or K. For the explanation of our observations new formation mechanisms are discussed.

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Section: Interpretation Of Variations and Implications For The Formatmentioning

confidence: 81%

Sporadic Ca and Ca<sup>+</sup> layers at mid-latitudes: Simultaneous observations and implications for their formation

et al. 2001

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“…Cox and Plane (1998) suggested an ion-molecule formation mechanism for sporadic Na layers, that was tested experimentally by Heinselman et al (1998) and Heinselman (2000). Clemesha et al (1999) concluded the ion-recombination mechanism to be the most likely cause for sporadic Na layers.…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

Development of the mesospheric Na layer at 69° N during the Geminids meteor shower 2010

et al. 2013

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Abstract. The ECOMA sounding rocket campaign in 2010 was performed to investigate the charge state and number density of meteoric smoke particles during the Geminids meteor shower in December 2010. The ALOMAR Na lidar contributed to the campaign with measurements of sodium number density, temperature and line-of-sight wind between 80 and 110 km altitude over Andøya in northern Norway. This paper investigates a possible connection between the Geminids meteor shower and the mesospheric sodium layer. We compare with data from a meteor radar and from a rocketborne in situ particle instrument on three days. Our main result is that the sodium column density is smaller during the Geminids meteor shower than the winter average at the same latitude. Moreover, during two of the three years considered, the sodium column density decreased steadily during these three weeks of the year. Both the observed decrease of Na column density by 30 % and of meteoric smoke particle column density correlate well with a corresponding decrease of sporadic meteor echoes. We found no correlation between Geminids meteor flux rates and sodium column density, nor between sporadic meteors and Na column density (R = 0.25). In general, we found the Na column density to be at very low values for winter, between 1.8 and 2.6 × 10 13 m −2 . We detected two meteor trails containing sodium, on 13 December 2010 at 87.1 km and on 19 December 2010 at 84 km. From these meteor trails, we estimate a global meteoric Na flux of 121 kg d −1 and a global total meteoric influx of 20.2 t d −1 .

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“…Whether or not these structures result in the formation of what would conventionally be called a sporadic layer would depend on the amplitude and, perhaps more importantly, the coherence of the wave responsible. In summary, we suggest that the following process takes place: sodium ions, trapped at the descending nodes in the winds associated with tides and/or gravity waves, are neutralized by processes of the sort described by Cox and Plane [1998], leading to the formation of descending peaks in sodium density. When the amplitude and coherence of the waves are appropriate, this process can lead to the formation of the narrow layers of very high density known as sporadic layers.…”

Section: Discussionmentioning

confidence: 99%

Vertical structure in the topside sodium layer

Clemesha¹,

Batista²,

Simonich³

1998

Geophysical Research Letters

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Abstract. It is shown that the assumption that sodium can be used as a passive tracer for studying atmospheric waves in the region above 90 km is not always valid. An analysis of wave structures observed in the sodium layer by lidar shows that the associated oscillations in the mixing ratio of sodium are frequently too large to be produced by vertical displacements in the presence of mixing ratio gradients. On some occasions these large amplitude oscillations appear to be associated with the formation of sporadic sodium layers, and it is suggested that both phenomena are most probably related to the windshear concentration of sodium ions.

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An ion‐molecule mechanism for the formation of neutral sporadic Na layers

Cited by 152 publications

References 62 publications

Sporadic Ca and Ca<sup>+</sup> layers at mid-latitudes: Simultaneous observations and implications for their formation

Sporadic Ca and Ca<sup>+</sup> layers at mid-latitudes: Simultaneous observations and implications for their formation

Development of the mesospheric Na layer at 69° N during the Geminids meteor shower 2010

Vertical structure in the topside sodium layer

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An ion‐molecule mechanism for the formation of neutral sporadic Na layers

Cited by 152 publications

References 62 publications

Sporadic Ca and Ca&lt;sup&gt;+&lt;/sup&gt; layers at mid-latitudes: Simultaneous observations and implications for their formation

Sporadic Ca and Ca&lt;sup&gt;+&lt;/sup&gt; layers at mid-latitudes: Simultaneous observations and implications for their formation

Development of the mesospheric Na layer at 69° N during the Geminids meteor shower 2010

Vertical structure in the topside sodium layer

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Product

Resources

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Sporadic Ca and Ca<sup>+</sup> layers at mid-latitudes: Simultaneous observations and implications for their formation

Sporadic Ca and Ca<sup>+</sup> layers at mid-latitudes: Simultaneous observations and implications for their formation