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Authors: Perna, L.*
Pezzopane, M.*
Zuccheretti, E.*
Fagundes, P. R.*
de Jesus, R.*
Cabrera, M. A.*
Ezquer, R. G.*
Title: Unusual nighttime impulsive foF2 enhancements at low latitudes: Phenomenology and possible explanations
Title of journal: Advances in space research
Series/Report no.: 3/54(2014)
Publisher: Elsevier Science Limited
Issue Date: 1-Aug-2014
DOI: 10.1016/j.asr.2013.05.014
Keywords: Equatorial ionosphere
Electron density enhancement
Traveling ionospheric disturbance
Fountain effect
Abstract: This paper is focused on unusual nighttime impulsive electron density enhancements that are rarely observed at low latitudes on a wide region of South America, under quiet and medium/high geomagnetic conditions. The phenomenon under investigation is very peculiar because besides being of brief duration, it is characterized by a pronounced compression of the ionosphere. The phenomenon was studied and analyzed using both the F2 layer critical frequency (foF2) and the virtual height of the base of the F region (h'F) values recorded at five ionospheric stations widely distributed in space, namely: Jicamarca (-12.0°, -76.8°, magnetic latitude -2.0°), Peru; Sao Luis (-2.6°, -44.2°, magnetic latitude +6.2°), Cachoeira Paulista (-22.4°, -44.6°, magnetic latitude -13.4°), and Sao Jose´ dos Campos (-23.2°, -45.9°, magnetic latitude -14.1°), Brazil; Tucumán (-26.9°, -65.4°, magnetic latitude -16.8°), Argentina. In a more restricted region over Tucumán, the phenomenon was also investigated by the total electron content (TEC) maps computed by using measurements from 12 GPS receivers. A detailed analysis of isoheight ionosonde plots suggests that traveling ionospheric disturbances (TIDs) caused by gravity wave (GW) propagation could play a significant role in causing the phenomenon both for quiet and for medium/high geomagnetic activity; in the latter case however a recharging of the fountain effect, due to electric fields penetrating from the magnetosphere, joins the TID propagation and plays an as much significant role in causing impulsive electron density enhancements.
Appears in Collections:05.07.02. Space weather
05.07.01. Solar-terrestrial interaction
05.01.03. Inverse methods
05.01.01. Data processing
05.01.99. General or miscellaneous
01.03.02. Magnetic storms
01.02.06. Instruments and techniques
01.02.05. Wave propagation
01.02.02. Dynamics
01.02.99. General or miscellaneous
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