Global transport and localized layering of metallic ions in the upper atmospherer

Carter, L. N.; Forbes, J. M.

doi:10.1007/s00585-999-0190-6

Cited by 92 publications

(62 citation statements)

References 68 publications

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“…First, the shape of the observed layers in Figures 2a and 4a indicates descending layers from higher to lower altitude as time progresses, similar to the motions of ion layers observed by the ISR . Secondly, the ratio of the wave crest and trough being far larger than any perturbations in the neutral atmosphere suggests that the Fe layers are related to ions that have been layered by various forces in the thermosphere [Carter and Forbes, 1999]. Thirdly, the changes of vertical wavelengths and phase speeds are similar to the TIDs [e.g., Djuth et al, 2010] and are consistent with theoretical expectations for gravity waves [Vadas, 2007;Vadas and Nicolls, 2009].…”

Section: Discussionsupporting

confidence: 69%

Lidar observations of neutral Fe layers and fast gravity waves in the thermosphere (110-155 km) at McMurdo (77.8°S, 166.7°E), Antarctica

Chu¹,

Yu²,

Gardner³

et al. 2011

Geophys. Res. Lett.

207

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We report the first lidar observations of neutral Fe layers with gravity wave signatures in the thermosphere from 110–155 km at McMurdo, Antarctica in May 2011. The thermospheric Fe densities are low, ranging from ∼200 cm−3 at 120 km to ∼20 cm−3 at 150 km. The measured temperatures from 115–135 km are considerably warmer than MSIS and appear to be related to Joule heating enhanced by aurora. The observed waves originate in the lower atmosphere and show periods of 1.5–2 h through 77–155 km. The vertical wavelength increases from ∼13 km at 115 km to ∼70 km at 150 km altitude. These wave characteristics are strikingly similar to the traveling ionospheric disturbances caused by internal gravity waves. The thermospheric Fe layers are likely formed through the neutralization of vertically converged Fe+ layers that descend in height following the gravity wave downward phase progression.

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Section: Discussionsupporting

confidence: 69%

Lidar observations of neutral Fe layers and fast gravity waves in the thermosphere (110-155 km) at McMurdo (77.8°S, 166.7°E), Antarctica

Chu¹,

Yu²,

Gardner³

et al. 2011

Geophys. Res. Lett.

207

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“…All this is in line with the windshear theory and numerical models (see e.g. Whitehead, 1989;Carter and Forbes, 1999), which predict metallic ion layer formation at vertical wind shear ion-convergence nodes.…”

Section: Introductionsupporting

confidence: 54%

Seasonal variability and descent of mid-latitude sporadic E layers at Arecibo

et al. 2009

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Abstract. Sporadic E layers (E s ) follow regular daily patterns in variability and altitude descent, which are determined primarily by the vertical tidal wind shears in the lower thermosphere. In the present study a large set of sporadic E layer incoherent scatter radar (ISR) measurements are analyzed. These were made at Arecibo (Geog. Lat. ∼18 • N; Magnetic Dip ∼50 • ) over many years with ISR runs lasting from several hours to several days, covering evenly all seasons. A new methodology is applied, in which both weak and strong layers are clearly traced by using the vertical electron density gradient as a function of altitude and time. Taking a time base equal to the 24-h local day, statistics were obtained on the seasonal behavior of the diurnal and semidiurnal tidal variability and altitude descent patterns of sporadic E at Arecibo. The diurnal tide, most likely the S(1,1) tide with a vertical wavelength around 25 km, controls fully the formation and descent of the metallic E s layers at low altitudes below 110 km. At higher altitudes, there are two prevailing layers formed presumably by vertical wind shears associated mainly with semidiurnal tides. These include: 1) a daytime layer starting at ∼130 km around midday and descending down to 105 km by local midnight, and 2) a less frequent and weaker nighttime layer which starts prior to midnight at ∼130 km, descending downwards at somewhat faster rate to reach 110 km by sunrise. The diurnal and semidiurnal-like pattern prevails, with some differences, in all seasons. The differences in occurrence, strength and descending speeds between the daytime and nighttime upper layers are not well understood from the present data alone and require further study.

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“…However, none of these investigated the differences in the distribution of Ca + from summer to winter and their relationship to Sporadic E. The data display modulation in the lower side of the layers, with a broader distribution seen during the summer as compared with winter. Simulation work by [Carter and Forbes, 1999] showed that winds have a greater effect on metallic ions than electric fields and also influences layering, which occurs mostly at the lower altitudes.…”

Section: Discussionmentioning

confidence: 99%

Summer to winter variability in mesospheric calcium ion distribution and its dependence on Sporadic E at Arecibo

et al. 2012

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[1] We present a new investigation of the variability in the metallic calcium ion concentration near the mesopause region, and its relation to the electron concentration during summer and winter seasons at the Arecibo Observatory. During the summer months the ion layer is broader, extending to 87-88 km compared with winter months where it occurs above this altitude around midnight. The concentration maximizes to $200 ions cm À3 around 90-95 km close to midnight during the summer. However, for the winter months, the peak occurs during the early morning hours in thin descending layers above 98 km. Summer to winter variation in the calcium ion to electron ratio displays an average value of $0.15 and 0.05 during these seasons, respectively. A good correlation between them suggests that Ca + densities are directly related to the strength of the Sporadic E, which is stronger in the summer. The average abundance of ions is 5.7 Â 10 7 cm À2 and 4.6 Â 10 7 cm À2 during summer and winter months respectively, while that for electrons is 1.2 Â 10 10 ions cm À2 and 5.8 Â 10 9 ion cm À2 for these seasons. Both Ca + and N e display strong descending layers at different altitudes during summer and winter. Calcium ion lifetimes against neutralization are a factor of two lower during the summer than in the winter months around 90 km but similar at altitudes exceeding 95 km.Citation: Raizada, S., C. A. Tepley, B. P. Williams, and R. García (2012), Summer to winter variability in mesospheric calcium ion distribution and its dependence on Sporadic E at Arecibo,

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Global transport and localized layering of metallic ions in the upper atmospherer

Cited by 92 publications

References 68 publications

Lidar observations of neutral Fe layers and fast gravity waves in the thermosphere (110-155 km) at McMurdo (77.8°S, 166.7°E), Antarctica

Lidar observations of neutral Fe layers and fast gravity waves in the thermosphere (110-155 km) at McMurdo (77.8°S, 166.7°E), Antarctica

Seasonal variability and descent of mid-latitude sporadic E layers at Arecibo

Summer to winter variability in mesospheric calcium ion distribution and its dependence on Sporadic E at Arecibo

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