scholarly journals Plasma irregularities in the tropical F-region detected by OI 7774 Å and 6300 Å nightglow measurements

1981 ◽  
Vol 86 (A5) ◽  
pp. 3496 ◽  
Author(s):  
Y. Sahai ◽  
J. A. Bittencourt ◽  
N. R. Teixeira ◽  
H. Takahashi
Keyword(s):  
Plasma Irregularities ◽  
F Region

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 A comparison of velocity measurements from the CUTLASS Finland radar and the EISCAT UHF system

1999 ◽  
Vol 17 (7) ◽  
pp. 892-902 ◽  
Author(s):  
J. A. Davies ◽  
M. Lester ◽  
S. E. Milan ◽  
T. K. Yeoman
Keyword(s):  
Total Duration ◽  
Field Of View ◽  
Simultaneous Occurrence ◽  
Plasma Convection ◽  
Contributing Factors ◽  
Plasma Irregularities ◽  
Incoherent Scatter ◽  
F Region ◽  
Initial Comparison ◽  
E Region

Abstract. The CUTLASS Finland radar, which comprises an integral part of the SuperDARN system of HF coherent radars, provides near continuous observations of high-latitude plasma irregularities within a field-of-view which extends over some four million square kilometres. Within the Finland radar field-of-view lie both the EISCAT mainland and EISCAT Svalbard incoherent scatter radar facilities. Since the CUTLASS Finland radar commenced operation, in February 1995, the mainland EISCAT UHF radar has been run in common programme 1 and 2 modes for a total duration exceeding 1000 h. Simultaneous and spatially coincident returns from these two radars over this period provide the basis for a comparison of irregularity drift velocity and F-region ion velocity. Initial comparison is limited to velocities from four intervals of simultaneous radar returns; intervals are selected such that they exhibit a variety of velocity signatures including that characteristic of the convection reversal and a rapidly fluctuating velocity feature. Subsequent comparison is on a statistical basis. The velocities measured by the two systems demonstrate reasonable correspondence over the velocity regime encountered during the simultaneous occurrence of coherent and incoherent scatter; differences between the EISCAT UHF measurements of F-region ion drift and the irregularity drift velocities from the Finland radar are explained in terms of a number of contributing factors including contamination of the latter by E-region echoes, a factor which is investigated further, and the potentially deleterious effect of discrepant volume and time sampling intervals.Key words. Ionosphere (ionospheric irregularities; plasma convection)

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 On developing a new ionospheric plasma index for Brazilian equatorial F region irregularities

2019 ◽  
Vol 37 (5) ◽  
pp. 807-818 ◽  
Author(s):  
Laysa Cristina Araujo Resende ◽  
Clezio Marcos Denardini ◽  
Giorgio Arlan Silva Picanço ◽  
Juliano Moro ◽  
Diego Barros ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Space Weather ◽  
Ionospheric Plasma ◽  
Monitoring Program ◽  
Plasma Irregularities ◽  
Plasma Drift ◽  
F Region ◽  
Maximum Value ◽  
Spread F

Abstract. F region vertical drifts (Vz) are the result of the interaction between ionospheric plasma with the zonal electric field and the Earth's magnetic field. Abrupt variations in Vz are strongly associated with the occurrence of plasma irregularities (spread F) during the nighttime periods. These irregularities are manifestations of space weather in the ionosphere's environment without necessarily requiring a solar burst. In this context, the Brazilian Space Weather Study and Monitoring Program (Embrace) of the National Institute for Space Research (INPE) has been developing different indexes to analyze these ionospheric irregularities in the Brazilian sector. Therefore, the main purpose of this work is to produce a new ionospheric scale based on the analysis of the ionospheric plasma drift velocity, named AV. It is based on the maximum value of Vz (Vzp), which in turn is calculated through its relationship with the virtual height parameter, h′F, measured by the Digisonde Portable Sounder (DPS-4D) installed in São Luís (2∘ S, 44∘ W; dip: −2.3∘). This index quantifies the time relationship between the Vz peak and the irregularity observed in the ionograms. Thus, in this study, we analyzed 7 years of data, between 2009 and 2015, divided by season in order to construct a standardized scale. The results show there is a delay of at least 15 min between the Vzp observation and the irregularity occurrence. Finally, we believe that this proposed index allows for evaluating the impacts of ionospheric phenomena in the space weather environment.

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 Structural characterization of the equatorial F region plasma irregularities in the multifractal context

2019 ◽  
Author(s):  
Neelakshi Joshi ◽  
Reinaldo R. Rosa ◽  
Siomel Savio ◽  
Esfhan Alam Kherani ◽  
Francisco Carlos de Meneses ◽  
...  
Keyword(s):  
Ionospheric Plasma ◽  
Fluctuation Analysis ◽  
Multifractal Detrended Fluctuation Analysis ◽  
Plasma Irregularities ◽  
In Situ Data ◽  
F Region ◽  
Linear Algorithms ◽  
Multiplicative Cascade

Abstract. In the emerging ionosphere-space-weather paradigm, investigating dynamical properties of ionospheric plasma irregularities using advanced computational non-linear algorithms is providing new insights into their turbulent-like nature, for instance, the evidence of energy distribution via multiplicative cascade. In this study, we present multifractal analysis of the equatorial F region in situ data obtained from two different experiments performed at Alcântara (2.4° S; 44.4° W), Brazil to explore their scaling structures. First experiment observed several large-medium scale plasma bubbles whereas second experiment observed vertical uplift of the base of F region. Multifractal detrended fluctuation analysis and p-model fit is used to analyze the plasma density fluctuation time series. Result shows presence of multifractality with degree of multifractality 0.53–1.1 with 0.29 ≤ p ≤ 0.4 cascading probability for first experiment. Another experimental data also exhibits multifractality with degree of multifractality 0.27–0.33 with 0.42 ≤ p ≤ 0.44 cascading probability in the ionospheric plasma irregularities. Our results confirm the nonhomogeneous nature of plasma irregularities and characterize the underlying nonhomogeneous multiplicative cascade hypothesis in the ionospheric medium. Differences in terms of scaling and complexity in data belonging to different types of phenomena are also addressed.

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