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)

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 Study of Equatorial Plasma Bubbles Using ASI and GPS Systems

2020 ◽  
Author(s):  
Dada P. Nade ◽  
Swapnil S. Potdar ◽  
Rani P. Pawar
Keyword(s):  
Electron Content ◽  
Gps Receiver ◽  
Plasma Bubble ◽  
Low Latitude ◽  
Total Electron ◽  
Plasma Irregularities ◽  
Plasma Bubbles ◽  
F Region ◽  
Equatorial Plasma Bubbles ◽  
Background Density

The plasma irregularities have been frequently observed in the F-region, at low latitude regions, due to the instability processes occurring in the ionosphere. The depletions in electron density, as compared to the background density, is a signature of the plasma irregularities. These irregularities are also known as the “equatorial plasma bubble” (EPB). These EPBs can measure by the total electron content (TEC) using GPS receiver and by images of the nightglow OI 630.0 nm emissions using all sky imager (ASI). The current chapter is based on the review on the signature of the EPBs in TEC and ASI. measurements. We have also discussed the importance of the study of EPBs.

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.

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 Instability mechanisms for the F‐region plasma irregularities inside the mid‐latitude ionospheric trough: Swarm observations

Space Weather ◽  
2021 ◽  
Author(s):  
Yiwen Liu ◽  
Chao Xiong ◽  
Xin Wan ◽  
Yeping Lai ◽  
Yuhao Wang ◽  
...  
Keyword(s):  
Plasma Irregularities ◽  
F Region ◽  
Region Plasma

scholarly journals Characteristics of ionospheric irregularities near the northern equatorial anomaly crest

2019 ◽  
Author(s):  
Jinghua Li ◽  
Guanyi Ma ◽  
Klemens Hocke ◽  
Qingtao Wan ◽  
Jiangtao Fan ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Ionospheric Irregularities ◽  
Lower Latitude ◽  
Occurrence Rate ◽  
Electron Content ◽  
Plasma Bubble ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Latitude Belt ◽  
Plasma Bubbles

Abstract. This paper detects the ionospheric irregularities with rate of total electron content (TEC) change index, ROTI from GPS observation at Taoyuan (24.95° N, 121.16° E) for the solar medium and minimum years of 2003 and 2008 in the declining phase of cycle 23, the solar maximum of 2014 in solar cycle 24. Local occurrence rate (LOR) is proposed to clarify the characteristics of the irregularities together with monthly occurrence rate (MOR) and ROTI maximum for 3 latitude belts, 20–23° N, 23–26° N, 26–29° N, around the equatorial anomaly crest. MOR in May/June is larger than those in equinoxes in 2008 and 2003, which is different from that of equatorial plasma bubbles. In 2014 although MOR maximum is observed in equinoxes, the MOR in May and June is much larger than that in September. Moreover, MORs in May to August at higher latitude belt 26–29° N are larger than those in lower latitude belts and smaller in the equinoxes. The latitudinal dependence of the LORs tends to be similar to that of MORs. Seasonal variations of LORs have a similar trend for different solar activities. Maximum LORs are observed in Feb/Mar and Sep/Oct, and moderate around June, which resemble those of plasma bubbles in seasonal variations, except for latitude belt 26–29° N where maximum LORs are seen in May–Jul. The seasonal variation of ROTI maximum conforms to that of the LOR. The results suggest that irregularities near the crest in May to August are mainly originated from nonequatorial process, which is more frequently happened but weaker than plasma bubble in both spatiotemporal scale and strength.

scholarly journals Anisotropy of ionospheric irregularities determined from the amplitude of satellite signals at a single receiver

1999 ◽  
Vol 17 (4) ◽  
pp. 508-518 ◽  
Author(s):  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
M. O. Kozlova ◽  
T. Nygrén
Keyword(s):  
Large Scale ◽  
Ground Level ◽  
Spatial Spectrum ◽  
Ionospheric Irregularities ◽  
Small Scale ◽  
Radio Waves ◽  
Large Scale Structures ◽  
F Region ◽  
Amplitude Fluctuations ◽  
A Chain

Abstract. A new method of determining the anisotropy parameters of small-scale irregularities in the ionospheric F region is presented and experimental results are shown. The method is based on observations of amplitude fluctuations of radio waves transmitted by satellites flying above the F region. In practice, Russian navigational satellites are used and both the amplitude and the phase of the received signal is measured on the ground level. The method determines both the field-aligned anisotropy and the field-perpendicular anisotropy and orientation of the spatial spectrum of the irregularities, assuming that the contours of constant power have an elliptic shape. A possibility of applying the method to amplitude tomography is also discussed. Using a chain of receivers on the ground level, one could locate the regions of small-scale irregularities as well as determine their relative intensities. Then the large-scale background structures could be mapped simultaneously by means of ordinary ray tomography using the phase observations, and therefore the relations of small-scale and large-scale structures could be investigated.Key words. Ionosphere (auroral ionosphere; ionospheric irregularities; instruments and techniques)

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