Equatorial F-Region Plasma Bubbles Studies

1997 ◽  
Author(s):  
P.R. Fagundes
Keyword(s):  
Plasma Bubbles ◽  
F Region ◽  
Region Plasma

Relationship between generation of equatorial F-region plasma bubbles and thermospheric dynamics

1995 ◽  
Vol 16 (5) ◽  
pp. 117-120 ◽  
Author(s):  
P.R Fagundes ◽  
Y Sahai ◽  
J.A Bittencourt ◽  
H Takahashi
Keyword(s):  
Plasma Bubbles ◽  
F Region ◽  
Thermospheric Dynamics ◽  
Region Plasma

scholarly journals Observations of day-to-day variability in precursor signatures to equatorial F-region plasma depletions

1999 ◽  
Vol 17 (8) ◽  
pp. 1053-1063 ◽  
Author(s):  
P. R. Fagundes ◽  
Y. Sahai ◽  
I. S. Batista ◽  
M. A. Abdu ◽  
J. A. Bittencourt ◽  
...  
Keyword(s):  
Large Scale ◽  
Imaging System ◽  
Diagnostic Techniques ◽  
Field Of View ◽  
Atmospheric Composition ◽  
Plasma Bubble ◽  
Plasma Bubbles ◽  
F Region ◽  
Good Sequence ◽  
Region Plasma

Abstract. In December 1995, a campaign was carried out to study the day-to-day variability in precursor signatures to large-scale ionospheric F-region plasma irregularities, using optical diagnostic techniques, near the magnetic equator in the Brazilian sector. Three instruments were operated simultaneously: (a) an all-sky (180° field of view) imaging system for observing the OI 630 nm nightglow emission at Alcântara (2.5°S, 44.4°W); (b) a digisonde (256-Lowell) at São Luis (2.6°S, 44.2°W); and (c) a multi-channel tilting filter-type zenith photometer for observing the OI 630 nm and mesospheric nightglow emissions at Fortaleza (3.9°S, 38.4°W). During the period December 14-18, 1995 (summer in the southern hemisphere), a good sequence of the OI 630 nm imaging observations on five consecutive nights were obtained, which are presented and discussed in this study. The observing period was geomagnetically quiet to moderate  (Kp = 0+ to 5+; Dst = 18 nT to -37 nT). On four nights, out of the five observation nights, the OI 630 nm imaging pictures showed formations of transequatorial north-south aligned intensity depletions, which are the optical signatures of large-scale ionospheric F-region plasma bubbles. However, considerable day-to-day variability in the onset and development of the plasma depleted bands was observed. On one of the nights it appears that the rapid uplifting of the F-layer in the post-sunset period, in conjunction with gravity wave activity at mesospheric heights, resulted in generation of very strong plasma bubble irregularities. One of the nights showed an unusual formation of north-south depleted band in the western sector of the imaging system field of view, but the structure did not show any eastward movement, which is a normal characteristic of plasma bubbles. This type of irregularity structure, which probably can be observed only by wide-angle imaging system, needs more investigations for a better understanding of its behaviour.Key words. Atmospheric composition and structure (airglow and aurora) · Ionosphere (equatorial ionosphere; ionospheric irregularities)

scholarly journals Equatorial F-region plasma depletion drifts: latitudinal and seasonal variations

2003 ◽  
Vol 21 (12) ◽  
pp. 2315-2322 ◽  
Author(s):  
A. A. Pimenta ◽  
P. R. Fagundes ◽  
Y. Sahai ◽  
J. A. Bittencourt ◽  
J. R. Abalde
Keyword(s):  
Large Scale ◽  
Ionospheric Irregularities ◽  
Plasma Bubble ◽  
Plasma Irregularities ◽  
Optical Instruments ◽  
Plasma Bubbles ◽  
F Region ◽  
Variation Characteristics ◽  
Wind Velocities ◽  
Region Plasma

Abstract. The equatorial ionospheric irregularities have been observed in the past few years by different techniques (e.g. ground-based radar, digisonde, GPS, optical instruments, in situ satellite and rocket instrumentation), and its time evolution and propagation characteristics can be used to study important aspects of ionospheric dynamics and thermosphere-ionosphere coupling. At present, one of the most powerful optical techniques to study the large-scale ionospheric irregularities is the all-sky imaging photometer system, which normally measures the strong F-region nightglow 630 nm emission from atomic oxygen. The monochromatic OI 630 nm emission images usually show quasi-north-south magnetic field-aligned intensity depletion bands, which are the bottomside optical signatures of large-scale F-region plasma irregularities (also called plasma bubbles). The zonal drift velocities of the plasma bubbles can be inferred from the space-time displacement of the dark structures (low intensity regions) seen on the images. In this study, images obtained with an all-sky imaging photometer, using the OI 630 nm nightglow emission, from Cachoeira Paulista (22.7° S, 45° W, 15.8° S dip latitude), Brazil, have been used to determine the nocturnal monthly and latitudinal variation characteristics of the zonal plasma bubble drift velocities in the low latitude (16.7° S to 28.7° S) region. The east and west walls of the plasma bubble show a different evolution with time. The method used here is based on the western wall of the bubble, which presents a more stable behavior. Also, the observed zonal plasma bubble drift velocities are compared with the thermospheric zonal neutral wind velocities obtained from the HWM-90 model (Hedin et al., 1991) to investigate the thermosphere-ionosphere coupling. Salient features from this study are presented and discussed.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric irregularities; instruments and techniques)

Spectral fluctuation analysis of ionospheric inhomogeneities over Brazilian territory. Part I: Equatorial F-region plasma bubbles

2016 ◽  
Vol 58 (10) ◽  
pp. 2037-2042 ◽  
Author(s):  
G. Fornari ◽  
R.R. Rosa ◽  
F.C. de Meneses ◽  
P. Muralikrishna
Keyword(s):  
Fluctuation Analysis ◽  
Plasma Bubbles ◽  
F Region ◽  
Region Plasma

scholarly journals Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 "Halloween Storms"

2009 ◽  
Vol 27 (12) ◽  
pp. 4463-4477 ◽  
Author(s):  
Y. Sahai ◽  
F. Becker-Guedes ◽  
P. R. Fagundes ◽  
A. J. de Abreu ◽  
R. de Jesus ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Ionospheric Irregularities ◽  
South American ◽  
The South ◽  
Geomagnetic Disturbances ◽  
Plasma Bubbles ◽  
F Region ◽  
A Chain ◽  
Ionospheric Sounding ◽  
Gps Observations

Abstract. The response of the ionospheric F-region in the South American sector during the super geomagnetic storms on 29 and 30 October 2003 is studied in the present investigation. In this paper, we present ionospheric sounding observations during the period 29–31 October 2003 obtained at Palmas (a near equatorial location) and Sao Jose dos Campos (a location under the southern crest of the equatorial ionospheric anomaly), Brazil, along with observations during the period 27–31 October 2003 from a chain of GPS stations covering the South American sector from Imperatriz, Brazil, to Rio Grande, Argentina. Also, complementary observations that include sequences of all-sky images of the OI 777.4 and 630.0 nm emissions observed at El Leoncito, Argentina, on the nights of 28–29 (geomagnetically quiet night) and 29–30 (geomagnetically disturbed night) October 2003, and ion densities observed in the South American sector by the DMSP F13, F14 and F15 satellites orbiting at about 800 km on 29 and 30 October 2003 are presented. In addition, global TEC maps derived from GPS observations collected from the global GPS network of International GPS Service (IGS) are presented, showing widespread and drastic TEC changes during the different phases of the geomagnetic disturbances. The observations indicate that the equatorial ionospheric irregularities or plasma bubbles extend to the Argentinean station Rawson (geom. Lat. 33.1° S) and map at the magnetic equator at an altitude of about 2500 km.

scholarly journals Electron heating by HF pumping of high-latitude ionospheric F-region plasma near magnetic zenith

2020 ◽  
Vol 38 (2) ◽  
pp. 297-307 ◽  
Author(s):  
Thomas B. Leyser ◽  
Björn Gustavsson ◽  
Theresa Rexer ◽  
Michael T. Rietveld
Keyword(s):  
Electron Temperature ◽  
Pump Beam ◽  
Electron Heating ◽  
Incoherent Scatter ◽  
F Region ◽  
Left Handed ◽  
Parameter Values ◽  
Uhf Radar ◽  
Region Plasma ◽  
Magnetic Zenith

Abstract. High-frequency electromagnetic pumping of ionospheric F-region plasma at high and mid latitudes gives the strongest plasma response in magnetic zenith, antiparallel to the geomagnetic field in the Northern Hemisphere. This has been observed in optical emissions from the pumped plasma turbulence, electron temperature enhancements, filamentary magnetic field-aligned plasma density irregularities, and in self-focusing of the pump beam in magnetic zenith. We present results of EISCAT (European Incoherent SCATter association) Heating-induced magnetic-zenith effects observed with the EISCAT UHF incoherent scatter radar. With heating transmitting a left-handed circularly polarized pump beam towards magnetic zenith, the UHF radar was scanned in elevation in steps of 1.0 and 1.5∘ around magnetic zenith. The electron energy equation was integrated to model the electron temperature and associated electron heating rate and optimized to fit the plasma parameter values measured with the radar. The experimental and modelling results are consistent with pump wave propagation in the L mode in magnetic zenith, rather than in the O mode.

scholarly journals Simultaneous observations of equatorial F-region plasma depletions over Brazil during the Spread-F Experiment (SpreadFEx)

2009 ◽  
Vol 27 (6) ◽  
pp. 2371-2381 ◽  
Author(s):  
P.-D. Pautet ◽  
M. J. Taylor ◽  
N. P. Chapagain ◽  
H. Takahashi ◽  
A. F. Medeiros ◽  
...  
Keyword(s):  
Gravity Wave ◽  
State University ◽  
Large Area ◽  
Plasma Bubbles ◽  
F Region ◽  
Equatorial Plasma Bubbles ◽  
Star Program ◽  
Spread F ◽  
Plasma Depletions ◽  
Bubble Characteristics

Abstract. From September to November 2005, the NASA Living with a Star program supported the Spread-F Experiment campaign (SpreadFEx) in Brazil to study the effects of convectively generated gravity waves on the ionosphere and their role in seeding Rayleigh-Taylor instabilities, and associated equatorial plasma bubbles. Several US and Brazilian institutes deployed a broad range of instruments (all-sky imagers, digisondes, photometers, meteor/VHF radars, GPS receivers) covering a large area of Brazil. The campaign was divided in two observational phases centered on the September and October new moon periods. During these periods, an Utah State University (USU) all-sky CCD imager operated at São João d'Aliança (14.8° S, 47.6° W), near Brasilia, and a Brazilian all-sky CCD imager located at Cariri (7.4° S, 36° W), observed simultaneously the evolution of the ionospheric bubbles in the OI (630 nm) emission and the mesospheric gravity wave field. The two sites had approximately the same magnetic latitude (9–10° S) but were separated in longitude by ~1500 km. Plasma bubbles were observed on every clear night (17 from Brasilia and 19 from Cariri, with 8 coincident nights). These joint datasets provided important information for characterizing the ionospheric depletions during the campaign and to perform a novel longitudinal investigation of their variability. Measurements of the drift velocities at both sites are in good agreement with previous studies, however, the overlapping fields of view revealed significant differences in the occurrence and structure of the plasma bubbles, providing new evidence for localized generation. This paper summarizes the observed bubble characteristics important for related investigations of their seeding mechanisms associated with gravity wave activity.

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