Variations of Sq foci position from the Indian longitudes and its influence on Equatorial Electrojet

Archana, R. K.; Arora, Kusumita

doi:10.1016/j.jastp.2022.105911

Cited by 2 publications

(8 citation statements)

References 36 publications

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“…In this study the CEJ is identified whenever the strength of EEJ goes below night time level with amplitude greater than 5 nT during 0600–1800LT (Archana & Arora, 2022). The observed CEJs for the pairs TIR‐HYB, TIR‐GH and TIR‐GAN are plotted in Figure 5.…”

Section: Observations and Resultsmentioning

confidence: 99%

“…Due to the presence of EEJ, the amplitudes of ∆H at TIR are always higher than those at HYB and GAN. The method used for extracting ∆H at the sites is described in Archana and Arora (2022). The amplitudes of ∆H at GAN are slightly higher than those at HYB for most of the days, and the differences in the amplitudes of ∆H between GAN and HYB is an indication of inter-hemispheric asymmetry of Sq.…”

Section: Data and Locations Of The Sitesmentioning

confidence: 99%

“…Similar observations were made by Vichare et al (2016), where a weak anti-correlation was observed with the latitudinal position of the Sq focus and EEJ strength. Recent observations by Archana and Arora (2022) reported that EEJ and CEJ amplitudes at TIR may be influenced by the movement of Sq foci from both hemispheres and are variable from season to season. Their study also reported a difference in EEJ amplitudes when derived using the pair TIR-GAN and TIR-HYB, where HYB and GAN are geomagnetic conjugate sites located around 8°N and 8°S of geomagnetic latitudes.…”

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confidence: 99%

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Re‐Visiting EEJ and CEJ Occurrences Pattern Under the Influence of Sq Variations of Both Hemispheres

2023

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The present study investigated the variability in Equatorial electrojet (EEJ) and Counter electrojet (CEJ) extracted at the Indian equatorial station Tirunelveli (TIR) using low‐latitude geomagnetic conjugate sites, Hyderabad (HYB) and GAN Island (GAN) from the northern and southern hemispheres respectively over a period of 5 years. A significant difference in the amplitudes, of more than 10 nT for 43% of the days, is observed when the TIR‐HYB pair and the TIR‐GAN pair are used. Occurrence of CEJs are 60% more when the TIR‐GAN pair is considered. A correlation coefficient of 0.9 is obtained between the monthly mean peaks of diurnal variations in H between TIR and GAN; this correlation coefficient is 0.66 between TIR and HYB. The correlation coefficients from the first principal components of H, at these sites show variability with seasons; the correlation observed between TIR and GAN is higher than that between TIR‐HYB for all seasons except northern winter. This indicates the coupling of EEJ with Sq of both northern or southern hemispheres with varying extents. The present study highlights that the extraction of EEJ/CEJ using Sq from only one hemisphere will lead to biased estimates; even a small difference in the seasonal pattern of ∆H at equatorial and low latitude sites can result in the over/under‐estimation of EEJ and hence CEJ.

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Section: Observations and Resultsmentioning

confidence: 99%

Section: Data and Locations Of The Sitesmentioning

confidence: 99%

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confidence: 99%

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Re‐Visiting EEJ and CEJ Occurrences Pattern Under the Influence of Sq Variations of Both Hemispheres

2023

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“…Recent studies by Archana and Arora (2022) and Archana et al. (2023) reported a significant difference in the amplitudes and seasonal pattern of Sq at low‐latitudes geomagnetic conjugate sites in the Indian sector.…”

Section: Introductionsmentioning

confidence: 96%

“…However, the highest total current intensity is observed around the equinox for both hemispheres (Matsushita, 1967; Matsushita & Maeda, 1965; Takeda, 2002). Recent studies by Archana and Arora (2022) and Archana et al. (2023) reported a significant difference in the amplitudes and seasonal pattern of Sq at low‐latitudes geomagnetic conjugate sites in the Indian sector.…”

Section: Introductionsmentioning

confidence: 96%

Variations of Inter‐Hemispheric Field‐Aligned Currents: Observations From Ground Geomagnetic Measurements

Archana,

Arora

2024

JGR Space Physics

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The east–west component of the geomagnetic field (Y‐component) at the Trivandrum (TRD) station, an equatorial site, is used to investigate the characteristics of Inter‐Hemispheric Field‐Aligned Currents (IHFACs) in the Indian sector during solar cycles 21 and 22. The observations reveal an annual variation of IHFAC in the dawn/noon sector with positive/negative peaks around northern summer. Furthermore, it is noted that IHFAC amplitudes are modulated by solar activity, superimposed with seasonal effects, with consistently higher amplitudes during the northern summer months. The dusk‐time IHFAC also shows a pattern modulated by seasons and solar cycles, with negative peaks around northern summer only during the low solar active years. The seasonal pattern of IHFAC shows a similar trend from April to September, where dawn/noon IHFAC is south/north directed, and for the remaining months, both are northward directed. The dusk‐side IHFAC is mostly south‐directed irrespective of the season. Moreover, it is demonstrated that the seasonal pattern of dawn and noon‐time IHFAC amplitudes show a strong to moderate correlation with amplitudes of Sq asymmetries between two hemispheres, but dusk‐time IHFAC does not follow this trend. The IHFAC directions at TRD follow the Fukushima model for May to September during the dawn‐noon sector for 70%–95% of the days and less than 50% of the days for remaining months. The noon‐dusk sector shows Fukushima model‐type polarity for ∼60% of days in June–July and less than 50% for remaining months. The global analysis of IHFAC, using monthly averages of hourly values from eight observatories spanning Asia, Africa, and America, reveals spatial differences in amplitude and directions. The directions of noon‐time IHFAC in the Indian‐East Asian and East‐African sectors follow similar trends, and the amplitude variations of noon‐time IHFAC can be explained by DE‐3 tidal effects. The IHFAC from the South American and West African sectors show intense southward and northward currents compared to other sites, indicating the influence of the South Atlantic Anomaly (SAA).

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Variations of Sq foci position from the Indian longitudes and its influence on Equatorial Electrojet

Cited by 2 publications

References 36 publications

Re‐Visiting EEJ and CEJ Occurrences Pattern Under the Influence of Sq Variations of Both Hemispheres

Re‐Visiting EEJ and CEJ Occurrences Pattern Under the Influence of Sq Variations of Both Hemispheres

Variations of Inter‐Hemispheric Field‐Aligned Currents: Observations From Ground Geomagnetic Measurements

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