scholarly journals The time delay between the Equatorial Ionization Anomaly and the Equatorial Electrojet in the eastern Asian and American sectors

2021 ◽  
Author(s):  
Jing Liu ◽  
Donghe Zhang ◽  
Yongqiang Hao ◽  
Zuo Xiao
Keyword(s):  
Time Delay ◽  
Equatorial Electrojet ◽  
Equatorial Ionization Anomaly

scholarly journals Investigation of the response time of the equatorial ionosphere in context of the equatorial electrojet and equatorial ionization anomaly

2011 ◽  
Vol 29 (7) ◽  
pp. 1267-1275 ◽  
Author(s):  
L. Jose ◽  
S. Ravindran ◽  
C. Vineeth ◽  
T. K. Pant ◽  
S. Alex
Keyword(s):  
Time Delay ◽  
Response Time ◽  
Large Scale ◽  
Equatorial Electrojet ◽  
Equatorial Ionosphere ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Equatorial Ionization Anomaly ◽  
Low Latitude Ionosphere

Abstract. Equatorial Electrojet (EEJ) and Equatorial Ionization Anomaly (EIA) are two large-scale processes in the equatorial/low latitude ionosphere, driven primarily by the eastward electric field during daytime. In the present paper we investigate the correlation between the Integrated EEJ strength (IEEJ) and the EIA parameters like the total electron content at the northern crest, location of crest in Magnetic latitude and strength of the EIA for the Indian sector. A good correlation has been observed between the IEEJ and EIA when a time delay is introduced between IEEJ and EIA parameters. This time delay is regarded as the response time of equatorial ionosphere in context of the evolution of EIA vis-à-vis EEJ. Further, a seasonal variation in the time delay has been observed, which is believed to be due to changes in thermospheric wind. Using the response time and the linear relationship obtained, the possibility of near-real time prediction of EIA parameters has been attempted and found that the prediction holds well during the geomagnetically quiet periods. The paper discusses these aspects in detail.

scholarly journals First results from ground-based daytime optical investigation of the development of the equatorial ionization anomaly

1996 ◽  
Vol 14 (2) ◽  
pp. 238-245 ◽  
Author(s):  
D. Pallam Raju ◽  
R. Sridharan ◽  
S. Gurubaran ◽  
R. Raghavarao
Keyword(s):  
Equatorial Electrojet ◽  
Equatorial Region ◽  
Optical Investigation ◽  
Optical Technique ◽  
Evolutionary Pattern ◽  
Equatorial Ionization Anomaly ◽  
First Results ◽  
Dip Equator ◽  
First Time ◽  
The Relationship

Abstract. A meridional scanning OI 630.0-nm dayglow photometer was operated from Ahmedabad (17.2°N dip lat.) scanning a region towards the south in the upper atmosphere extending over ~5° in latitude from 10.2°N to 15.2°N dip latitude. From the spatial and temporal variabilities of the dayglow intensity in the scanning region we show for the first time, evidence for the passage of the crest of the equatorial ionization anomaly (EIA) in the daytime by means of a ground-based optical technique. The relationship between the daytime eastward electric field over the dip equator in the same longitude zone as inferred from the equatorial electrojet strength and the evolutionary pattern of EIA is clearly demonstrated. The latter as inferred from the dayglow measurements is shown to be consistent with our present understanding of the electrodynamical processes in the equatorial region. The present results reveal the potential of this ground-based optical technique for the investigation of ionospheric/thermospheric phenomena with unprecedented spatial and temporal resolution.

scholarly journals Day-to-day variability of equatorial electrojet and its role on the day-to-day characteristics of the equatorial ionization anomaly over the Indian and Brazilian sectors

2015 ◽  
Vol 120 (10) ◽  
pp. 9117-9131 ◽  
Author(s):  
K. Venkatesh ◽  
P. R. Fagundes ◽  
D. S. V. V .D. Prasad ◽  
C. M. Denardini ◽  
A. J. de Abreu ◽  
...  
Keyword(s):  
Equatorial Electrojet ◽  
Equatorial Ionization Anomaly

scholarly journals Observations of equatorial ionization anomaly over Africa and Middle East during a year of deep minimum

2017 ◽  
Vol 35 (1) ◽  
pp. 123-132 ◽  
Author(s):  
Olawale Bolaji ◽  
Oluwafisayo Owolabi ◽  
Elijah Falayi ◽  
Emmanuel Jimoh ◽  
Afolabi Kotoye ◽  
...  
Keyword(s):  
Middle East ◽  
Continuity Equation ◽  
Equatorial Electrojet ◽  
Data Acquisition System ◽  
Magnetic Data ◽  
Electron Content ◽  
Deep Minimum ◽  
Total Electron ◽  
Equatorial Ionization Anomaly ◽  
Low Latitudes

Abstract. In this work, we investigated the veracity of an ion continuity equation in controlling equatorial ionization anomaly (EIA) morphology using total electron content (TEC) of 22 GPS receivers and three ground-based magnetometers (Magnetic Data Acquisition System, MAGDAS) over Africa and the Middle East (Africa–Middle East) during the quietest periods. Apart from further confirmation of the roles of equatorial electrojet (EEJ) and integrated equatorial electrojet (IEEJ) in determining hemispheric extent of EIA crest over higher latitudes, we found some additional roles played by thermospheric meridional neutral wind. Interestingly, the simultaneous observations of EIA crests in both hemispheres of Africa–Middle East showed different morphology compared to that reported over Asia. We also observed interesting latitudinal twin EIA crests domiciled at the low latitudes of the Northern Hemisphere. Our results further showed that weak EEJ strength associated with counter electrojet (CEJ) during sunrise hours could also trigger twin EIA crests over higher latitudes.

scholarly journals Quasi-16-day periodic meridional movement of the equatorial ionization anomaly

2014 ◽  
Vol 32 (2) ◽  
pp. 121-131 ◽  
Author(s):  
X. H. Mo ◽  
D. H. Zhang ◽  
L. P. Goncharenko ◽  
Y. Q. Hao ◽  
Z. Xiao
Keyword(s):  
Large Scale ◽  
Maximum Amplitude ◽  
Equatorial Electrojet ◽  
Peak Height ◽  
Periodic Component ◽  
Low Latitude ◽  
Latitude Belt ◽  
Equatorial Ionization Anomaly ◽  
Periodic Movement ◽  
Atmospheric Variations

Abstract. Based on the daytime location of the equatorial ionization anomaly (EIA) crest derived from GPS observations at low latitude over China during the 2005–2006 stratospheric sudden warming (SSW), a quasi-16-day periodic meridional movement of EIA crest with the maximum amplitude of about 2 degrees relative to the average location of EIA crest has been revealed. In addition, periodic variations that are in phase with the meridional EIA movement are also revealed in the equatorial electrojet (EEJ) and F2 layer peak height (hmF2) over Chinese ionosonde stations Haikou and Chongqing. The quasi-16-day periodic component in Dst index is weak, and the 16-day periodic component does not exist in F10.7 index. Such large-scale periodic meridional movement of EIA crest is likely related to the globally enhanced stratospheric planetary waves coupled with anomalous stratospheric zonal wind connected with SSW. In addition, such large-scale periodic movement of EIA should be global, and can affect the ionospheric morphology around the low-latitude belt near the EIA region. Further case analysis, simulation and theoretical studies must proceed in order to understand the periodic movements of EIA connected with the different periodic atmospheric variations.

scholarly journals High resolution 2-D maps of OI 630.0 nm thermospheric dayglow from equatorial latitudes

1998 ◽  
Vol 16 (8) ◽  
pp. 997-1006
Author(s):  
D. Pallam Raju ◽  
R. Sridharan
Keyword(s):  
High Resolution ◽  
Gravity Waves ◽  
Large Scale ◽  
Equatorial Electrojet ◽  
Equatorial Ionosphere ◽  
Atmospheric Composition ◽  
Scale Feature ◽  
Equatorial Ionization Anomaly ◽  
Composition And Structure ◽  
Instruments And Techniques

Abstract. The first-ever high resolution 2-D maps of OI 630.0 nm dayglow obtained from equatorial latitudes clearly reveal the movement as a large-scale feature of the equatorial ionization anomaly (EIA). These also show the presence of wave-like features classified as gravity waves presumably originating at the crest of the EIA, similar to the equatorial electrojet acting as a source of these waves. These results are presented and discussed.Key words. Atmospheric composition and structure (Airglow and aurora) · Ionosphere (Equatorial ionosphere; Instruments and techniques).

scholarly journals The combined effects of electrojet strength and the geomagnetic activity (<I>K<sub>p</sub></I>-index) on the post sunset height rise of the F-layer and its role in the generation of ESF during high and low solar activity periods

2007 ◽  
Vol 25 (9) ◽  
pp. 2007-2017 ◽  
Author(s):  
S. Tulasi Ram ◽  
P. V. S. Rama Rao ◽  
D. S. V. V. D. Prasad ◽  
K. Niranjan ◽  
A. Raja Babu ◽  
...  
Keyword(s):  
Solar Activity ◽  
Density Gradient ◽  
Geomagnetic Activity ◽  
Equatorial Electrojet ◽  
Peak Height ◽  
Linear Growth Rate ◽  
Combined Effects ◽  
Equatorial Station ◽  
Plasma Bubbles ◽  
Equatorial Ionization Anomaly

Abstract. Several investigations have been carried out to identify the factors that are responsible for the day-to-day variability in the occurrence of equatorial spread-F (ESF). But the precise forecasting of ESF on a day-to-day basis is still far from reality. The nonlinear development and the sustenance of ESF/plasma bubbles is decided by the background ionospheric conditions, such as the base height of the F-layer (h'F), the electron density gradient (dN/dz), maximum ionization density (Nmax), geomagnetic activity and the neutral dynamics. There is increasing evidence in the literature during the recent past that shows a well developed Equatorial Ionization Anomaly (EIA) during the afternoon hours contributes significantly to the initiation of ESF during the post-sunset hours. Also, there exists a good correlation between the Equatorial Ionization Anomaly (EIA) and the Integrated Equatorial ElectroJet (IEEJ) strength, as the driving force for both is the same, namely, the zonal electric field at the equator. In this paper, we present a linear relationship that exists between the daytime integrated equatorial electrojet (IEEJ) strength and the maximum elevated height of the F-layer during post-sunset hours (denoted as peak h'F). An inverse relationship that exists between the 6-h average Kp-index prior to the local sunset and the peak h'F of the F-layer is also presented. A systematic study on the combined effects of the IEEJ and the average Kp-index on the post-sunset, peak height of the F-layer (peak h'F), which controls the development of ESF/plasma bubbles, is carried out using the ionosonde data from an equatorial station, Trivandrum (8.47° N, 76.91° E, dip.lat. 0.5° N), an off-equatorial station, SHAR (13.6° N, 79.8° E, dip.lat. 10.8° N) and VHF scintillations (244 MHz) observed over a nearby low-latitude station, Waltair (17.7° N, 83.3° E, dip.lat. 20° N). From this study, it has been found that the threshold base height of the F-layer at the equator for the development of plasma bubbles is reduced from 405 km to 317 km as the solar activity decreases from March 2001 (mean Rz=113.5) to March 2005 (mean Rz=24.5). This decrease in threshold height with the decreasing solar activity is explained on the basis of changes in the local linear growth rate of the collisional Rayleigh-Taylor instability, due to the variability of various terms such as inverse density gradient scale length (L−1), ion-neutral collision frequency (νin) and recombination rate (R) with the changes in the solar activity.

Variability of the African equatorial ionization anomaly (EIA) crests during the year 2013

2019 ◽  
Vol 97 (2) ◽  
pp. 155-165 ◽  
Author(s):  
P.O. Amaechi ◽  
E.O. Oyeyemi ◽  
A.O. Akala
Keyword(s):  
Extreme Ultraviolet ◽  
Correlation Coefficients ◽  
Equatorial Electrojet ◽  
Magnetic Equator ◽  
Electron Content ◽  
Total Electron ◽  
Total Electron Content Data ◽  
Equatorial Ionization Anomaly ◽  
A Chain ◽  
Year 2013

This paper discusses the variability of the position and magnitude of the crests of African Equatorial Ionization Anomaly during noon and post sunset periods. Total electron content data covered the year 2013, and were obtained from a chain of global positioning system receivers in both hemispheres around 37°E longitude. Local magnetometer data were used to infer the direction and magnitude of the E × B drift, while the solar extreme ultraviolet proxy index was used as a measure of solar activity. It was found that the time of formation of both crests varied from 1400 to 1700 local time. Additionally, the position of the crests was found to be asymmetric with respect to the magnetic equator. During the noon period, the position of the northern and southern crests varied from 4.91° to 7.36° and −9.17° to −12.62°, respectively. During the post-sunset period, it varied from 8° to 11.7° and −9° to −16°, respectively. Seasonally, with reference to the magnetic equator, both crests moved poleward during equinoxes and collapsed towards the equator during winter and summer. Equinoxes recorded the greatest crest magnitude followed by winter then summer over both hemispheres during the noon period. However, this trend persisted over the northern crest only during the post-sunset period. Overall, during the noon period, we recorded correlation coefficients of 0.67 and 0.68 between crest magnitudes and ΔH, a proxy for equatorial electrojet current, and 0.88 and 0.81 between crest positions and ΔH, for the northern and southern crests, respectively. During the Halloween day storm of 30 October 2013, a westward electric field inhibited the development of the post-sunset crests.

scholarly journals Latitude-dependent delay in the responses of the equatorial electrojet and <i>S</i><sub><i>q</i></sub> currents to X-class solar flares

2018 ◽  
Vol 36 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Paulo A. B. Nogueira ◽  
Mangalathayil A. Abdu ◽  
Jonas R. Souza ◽  
Clezio M. Denardini ◽  
Paulo F. Barbosa Neto ◽  
...  
Keyword(s):  
Time Delay ◽  
Electric Field ◽  
Solar Flares ◽  
Extreme Ultraviolet ◽  
Equatorial Electrojet ◽  
Peak Effect ◽  
X Rays ◽  
Low Latitude ◽  
Conductivity Enhancement ◽  
Ionosphere Model

Abstract. We have analyzed low-latitude ionospheric current responses to two intense (X-class) solar flares that occurred on 13 May 2013 and 11 March 2015. Sudden intensifications, in response to solar flare radiation impulses, in the Sq and equatorial electrojet (EEJ) currents, as detected by magnetometers over equatorial and low-latitude sites in South America, are studied. In particular we show for the first time that a 5 to 8 min time delay is present in the peak effect in the EEJ, with respect that of Sq current outside the magnetic equator, in response to the flare radiation enhancement. The Sq current intensification peaks close to the flare X-ray peak, while the EEJ peak occurs 5 to 8 min later. We have used the Sheffield University Plasmasphere-Ionosphere Model at National Institute for Space Research (SUPIM-INPE) to simulate the E-region conductivity enhancement as caused by the flare enhanced solar extreme ultraviolet (EUV) and soft X-rays flux. We propose that the flare-induced enhancement in neutral wind occurring with a time delay (with respect to the flare radiation) could be responsible for a delayed zonal electric field disturbance driving the EEJ, in which the Cowling conductivity offers enhanced sensitivity to the driving zonal electric field. Keywords. Ionosphere (equatorial ionosphere)

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