A study of the role of ion–molecule chemistry in the formation of sporadic sodium layers

Collins, S.; Plane, J. M. C.; Kelley, M. C.; Wright, Timothy G.; Soldán, Pavel; Kane, Timothy J.; Gerrard, A. J.; Grime, Brent W.; Rollason, R. J.; Friedman, J. S.; González, S. A.; Zhou, Qihou; Sulzer, M. P.; Tepley, C. A.

doi:10.1016/s1364-6826(02)00129-3

Cited by 78 publications

(80 citation statements)

References 46 publications

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“…The current best theory for the formation of sporadic sodium layers is that sodium ions are concentrated by wind shears interacting with the electrodynamics to form a narrow ion layer, which is then pushed downwards with the downward phase propagation of most waves and tides (Cox and Plane, 1998;Collins et al, 2002). The chemical lifetime of Na + decreases rapidly with decreasing height.…”

Section: Introductionmentioning

confidence: 99%

“…When the Na + is pushed to an altitude where the chemical lifetime is short enough, the Na + is converted into atomic Na, which is then detected as a narrow layer by the lidar. The height of conversion ranges from roughly 103 to 95 km, depending on a number of factors such as atomic oxygen concentration and temperature (Collins et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Coincident extremely large sporadic sodium and sporadic E layers observed in the lower thermosphere over Colorado and Utah

et al. 2007

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Abstract. On the night of 2 June 2002, the sodium lidar in Fort Collins, CO (40.6 N, 105 W) measured an extremely strong sporadic sodium layer lasting from 03:30 to 05:00 UT with several weaker layers later in the night at 06:00 and 09:00 UT. There is a double layer structure with peaks at 101 and 104 km. The peak sodium density was 21 000 atoms/cm3 with a column abundance of up to twice that of the normal sodium layer. The peak density was 500 times greater than the typical density at that altitude. The sporadic layer abundance and strength factor were higher than any reported in the literature. The two lidar beams, separated by 70 km at this altitude, both measured 0.6 h periodicities in the abundance, but out of phase with each other by 0.3 h. There is also evidence for strong wave activity in the lidar temperatures and winds. The NOAA ionosonde in Boulder, CO (40.0 N, 105 W) measured a critical frequency (foEs) of 14.3 MHz at 03:00 UT on this night, the highest value anytime during 2002. The high values of total ion density inferred means that Na+ fraction must have been only a few percent to explain the neutral Na layer abundances. The Bear Lake, Utah (41.9 N, 111.4 W) dynasonde also measured intense Es between 02:00 and 05:00 UT and again from 06:00 to 08:00 UT about 700 km west of the lidar, with most of the ionograms during these intervals measuring Es up to 12 MHz, the limit of the ionosonde sweep. Other ionosondes around North America on the NGDC database measured normal foEs values that night, so it was a localized event within North America. The peak of Es activity observed in Europe during the summer of 2002 occurred on 4 June. The observations are consistent with the current theories where a combination of wind shears and long period waves form and push downward a concentrated layer of ions, which then chemically react and form a narrow layer of sodium atoms.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coincident extremely large sporadic sodium and sporadic E layers observed in the lower thermosphere over Colorado and Utah

et al. 2007

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“…The Na·N 2 + formation is quite weak, and it reacts with CO 2 to become Na·CO 2 + . These cluster ions are neutralized with a dissociative electron to form neutral Na [Collins et al, 2002]. Thus, the sodium density will increase if a sporadic E layer exists [Plane, 2003].…”

Section: 1002/2015ja021339mentioning

confidence: 99%

“…The complex sodium chemical process has been explained by Cox and Plane [1998] and Collins et al [2002]. Above 90 km, Na atoms are ionized mostly by NO + and O 2 + ions.…”

Section: Temperature Mechanismmentioning

confidence: 99%

“…And a less pronounced link, or absence of a link, between Es and SSL is observed below 95 km [Hansen and Von Zahn, 1990]. Second, the complex SSL chemical process has been published [Cox and Plane, 1998;Collins et al, 2002;Plane, 2003Plane, , 2004 while SSLs and temperature have been observed simultaneously [Hansen and Von Zahn, 1990;Gardner et al, 1993Gardner et al, , 1995Batista et al, 2002]. Temperature-independent conjecture Zhou and Mathews, 1995] and modeling [Delgado et al, 2012] along with sporadic neutral metal atom layers have been studied and discussed.…”

Section: Introductionmentioning

confidence: 98%

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Sodium lidar‐observed gravity wave breaking followed by an upward propagation of sporadic sodium layer over Hefei, China

Ban

Fang

et al. 2015

JGR Space Physics

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The University of Science and Technology of China sodium temperature/wind lidar observed a strong zonal wind shear (~60 m/s/km) near 98 km between 1315 and 1330 UT on 29 July 2013 and a cooling near 96–100 km (above a warming near 90–95 km) between 1330 and 1430 UT. This suggests a possible gravity wave (GW) breaking event. Comparison of the lidar results with observations from a nearby meteor radar and with satellite results indicated that the GW likely broke down over a large horizontal area. In addition, the sodium number density suddenly increased 10–12 times (∼13, 000atm/cm3) near 95 km at 1400 UT, immediately following the GW breaking. This sporadic sodium layer (SSL), which is different from most previously observed SSL events (which propagate downward), tended to propagate upward and also appeared ~2 min earlier in the west channel than in the east channel. The horizontal propagation direction of the SSL was aligned with the horizontal wind direction, which was likely due to the propagation of a high‐density sodium layer from the northwest of the lidar site, and was possibly related to the earlier GW breaking event.

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First simultaneous measurements of Na and K thermospheric layers along with TILs from Arecibo

Raizada

Brum

Tepley

et al. 2015

Geophysical Research Letters

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This work presents the first simultaneous observations of Na and K between 120 and 150 km altitudes along with ionospheric tidal ion layers (TILs) obtained on 30 January 2006 data from Arecibo. The latter displays an average downward phase velocity of ~14.7 ms−1. However, the neutral layers descend together at a much slower velocity of about ~0.69 ms−1. This indicates that thermospheric atomic metal layers are not necessarily associated with TILs. The ratio of the average Na/K abundances in thermosphere is ~35.5 as compared to 150 in the main layer (80–105 km). The long lifetimes of ions at ~140 km implies that neutral layers cannot result from direct neutralization of metal ions in the TILs. We investigate different mechanisms that can deposit neutral atoms at thermospheric altitudes.

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A study of the role of ion–molecule chemistry in the formation of sporadic sodium layers

Cited by 78 publications

References 46 publications

Coincident extremely large sporadic sodium and sporadic E layers observed in the lower thermosphere over Colorado and Utah

Coincident extremely large sporadic sodium and sporadic E layers observed in the lower thermosphere over Colorado and Utah

Sodium lidar‐observed gravity wave breaking followed by an upward propagation of sporadic sodium layer over Hefei, China

First simultaneous measurements of Na and K thermospheric layers along with TILs from Arecibo

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