Anomalous night-time peaks in diurnal variations of NmF2 close to the geomagnetic equator: A statistical study

Павлов, А. В.; Павлова, Н. М.

doi:10.1016/j.jastp.2007.07.003

Cited by 23 publications

(21 citation statements)

References 29 publications

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“…The postmidnighttime of occurrence of this enhancement along with its very short duration and the associated compression of the ionosphere makes this event very distinctive. Also, the fact that the nighttime enhancement investigated in this paper occurred during geomagnetically quiet conditions is quite significant because recently Pavlov and Pavlova [2007] found that this kind of phenomena occur mainly during geomagnetically disturbed conditions.…”

Section: Discussionmentioning

confidence: 77%

“…It is well‐known that the nighttime values of fo F2 and total electron content (TEC) do not always decrease smoothly. Several authors performed statistical studies on Nm F2 and TEC enhancements at midlatitudes and low latitudes [ Janve et al , 1979; Balan and Rao , 1987; Lois et al , 1990; Balan et al , 1991, 1994; Su et al , 1994; Mikhailov et al , 2000a; Farelo et al , 2002; Pavlov and Pavlova , 2007; Luan et al , 2008].…”

Section: Introductionmentioning

confidence: 99%

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Unusual nighttime impulsivefoF2 enhancement below the southern anomaly crest under geomagnetically quiet conditions

Pezzopane

Fagundes

Ciraolo³

et al. 2011

J. Geophys. Res.

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An unusual nighttime impulsive electron density enhancement was observed on 6 March 2010 over a wide region of South America, below the southern crest of the equatorial anomaly, under low solar activity and quiet geomagnetic conditions. The phenomenon was observed almost simultaneously by the F2 layer critical frequency (foF2) recorded at three ionospheric stations which are widely distributed in space, namely Cachoeira Paulista (22.4°S, 44.6°W, magnetic latitude 13.4°S), São José dos Campos (23.2°S, 45.9°W, magnetic latitude 14.1°S), Brazil, and Tucumán (26.9°S, 65.4°W, magnetic latitude 16.8°S), Argentina. Although in a more restricted region over Tucumán, the phenomenon was also observed by the total electron content (TEC) maps computed by using measurements from 12 GPS receivers. The investigated phenomenon is very particular because besides being of brief duration, it is characterized by a pronounced compression of the ionosphere. This compression was clearly visible both by the virtual height of the base of the F region (h′F) recorded at the aforementioned ionospheric stations, and by both the vertical electron density profiles and the slab thickness computed over Tucumán. Consequently, neither an enhanced fountain effect nor plasma diffusion from the plasmasphere can be considered as the single cause of this unusual event. A thorough analysis of isoheight and isofrequency ionosonde plots suggest that traveling ionospheric disturbances (TIDs) caused by gravity wave (GW) propagation could have likely played a significant role in causing the phenomenon.

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Section: Discussionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Unusual nighttime impulsivefoF2 enhancement below the southern anomaly crest under geomagnetically quiet conditions

Pezzopane

Fagundes

Ciraolo³

et al. 2011

J. Geophys. Res.

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“…Such identifications have been taken by Jain et al . [], Pavlov and Pavlova [], and Pirog et al . [].…”

Section: Nighttime Enhancement Event Identificationmentioning

confidence: 99%

A case study of postmidnight enhancement in F‐layer electron density over Sanya of China

et al. 2013

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[1] The electron density in the ionospheric F region occasionally stops its decay and rises pronouncedly during night hours, which are termed ionospheric nighttime enhancements. In this case study, we analyzed the manually scaled ionogram records measured by a Lowell DPS-4D ionosonde operated at Sanya (18.3°N, 109.6°E), China, to explore postmidnight enhancement events occurred in 2012, a year of moderate solar activities. Common features in these cases illustrate that, accompanying nighttime rises in peak electron density of F2 layer (NmF2), the height of F2 layer is depressed significantly, and the ionogram-derived electron density height profiles become thinner. There are time shifts in the development of electron density enhancements in the F layer; that is, enhancement develops earlier and reaches peaks earlier at higher altitudes than at lower altitudes. Meanwhile, plasma drift is detected downward under such events, revealing the essential role of the westward electric field in forming the postmidnight enhancements in electron density of ionospheric F layer at such low latitudes.

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“…The solar-produced ionospheric electron density is generally expected to decay steadily during nighttime, because the most important ionization source, the solar extreme ultraviolet radiation, is absent during nighttime. However, it has long been realized that the electron density in the ionosphere may not decrease throughout the night as predicted by the simple theory but show some enhancements under various geophysical conditions [e.g., Young et al, 1970;Davies et al, 1979;Balan and Rao, 1987;Jakowski et al, 1991;Balan et al, 1994;Su et al, 1994;Unnikrishnan et al, 2002;Farelo et al, 2002;Horvath, 2006;Pavlov and Pavlova, 2007;Luan et al, 2008;He et al, 2009;Yakovets et al, 2009]. This phenomenon is called ionospheric nighttime enhancements.…”

Section: Introductionmentioning

confidence: 99%

Modeling study of nighttime enhancements in F region electron density at low latitudes

Liu

Chen

et al. 2014

JGR Space Physics

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In this paper we carry out case-control simulations to examine the mechanisms of the nighttime anomalous enhancements in electron density in the ionosphere at low latitudes, which were studied earlier in another research. The results confirm the earlier conclusion that the downward E × B plasma drift due to westward electric field at night is the main driving force for the nighttime enhancement. In addition, the phase of the electric field is found important in forming the enhancement. Delayed westward electric field can produce significant postmidnight enhancement as observed at Sanya (geomagnetic latitude: 8.2°N). In addition, the equatorward neutral wind at night is found to modulate the formation of the nighttime enhancement at geomagnetic latitudes below 15°N. The combined effects of the two drivers cause significant equatorward/downward plasma flux, which results in the enhancement of electron density as well as the drop in ionospheric peak height.

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Anomalous night-time peaks in diurnal variations of NmF2 close to the geomagnetic equator: A statistical study

Cited by 23 publications

References 29 publications

Unusual nighttime impulsivefoF2 enhancement below the southern anomaly crest under geomagnetically quiet conditions

Unusual nighttime impulsivefoF2 enhancement below the southern anomaly crest under geomagnetically quiet conditions

A case study of postmidnight enhancement in F‐layer electron density over Sanya of China

Modeling study of nighttime enhancements in F region electron density at low latitudes

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