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Published: 6 September 2023

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1

Rastogi, R. G. "Meridional equatorial electrojet current in the American sector." Annales Geophysicae 17, no. 2 (February 28, 1999): 220–30. http://dx.doi.org/10.1007/s00585-999-0220-4.

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Abstract. Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H) is associated with a simultaneous increase of eastward geomagnetic field (Y). It is shown that during the counter electrojet period when ∆H is negative, ∆Y also becomes negative. Thus, the diurnal variation of ∆Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej). At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej), a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.Key words. Geomagnetism and paleomagnetism (dynamo theories) · Ionosphere (equatorial ionosphere; ionosphere disturbances)

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2

Reddy, C. A. "The equatorial electrojet." Pure and Applied Geophysics PAGEOPH 131, no. 3 (1989): 485–508. http://dx.doi.org/10.1007/bf00876841.

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3

Klimenko, M. V., V. V. Klimenko, and V. V. Bryukhanov. "Numerical modeling of the equatorial electrojet UT-variation on the basis of the model GSM TIP." Advances in Radio Science 5 (June 13, 2007): 385–92. http://dx.doi.org/10.5194/ars-5-385-2007.

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Abstract. In the presented work the results of numerical modeling of the UT-variation of the equatorial electrojet, executed on the basis of the model GSM TIP are presented, taking into account the dynamo electric fields generated by thermospheric winds in a current-carrying layer of the ionosphere at heights 80–175 km above a surface of the Earth. To the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP), developed in WD IZMIRAN, a new block for the calculation of electric fields in the ionosphere has been added. In this block the solution of the three-dimensional equation describing the conservation law of the full current in the Earth's ionosphere is reduced to the solution of the two-dimensional equation by integration along geomagnetic field lines. Calculations of parameters of the near-Earth space plasmas have been executed for quiet equinoctial conditions on 22 March 1987 during the minimum of solar activity. It has been shown, that there is a distinct semidiurnal harmonic in the diurnal behavior of the linear density of the equatorial electrojet with maxima at 23:00 UT and 15:00 UT, as well as with minima at 06:00 UT and 20:00 UT. The greatest and smallest values of the peak intensity of the equatorial electrojet with respect to the diurnal behavior can differ by a factor of two. The longitudinal extent of the area of the equatorial electrojet does hardly show any UT-variation, but the greatest longitudinal extent is at 06 UT. With the growth of the peak intensity of the equatorial electrojet its latitudinal extent also increases (on ~5–10°) a little. At the same time the equatorial electrojet in the maxima of intensity has approximately an identical width, whereas in the minima the electrojet is narrow in the morning and wide in the afternoon. As for the surface density of the equatorial electrojet, its UT-variation is much weaker and equals ~1–3 A/km2 and the peak intensity is equal ~15–20 A/km2. The latitudinal extent of the surface density of the equatorial electrojet is maximal at 23:00 UT and 15:00 UT and minimal at 06:00 UT and 20:00 UT.

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4

Ugwu, Ernest Benjamin Ikechukwu, and Christopher Ekene Okeke. "On the Variation of Geomagnetic H-Component during Solar Quiet Days." European Journal of Applied Physics 3, no. 2 (March 25, 2021): 11–15. http://dx.doi.org/10.24018/ejphysics.2021.3.2.35.

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The hourly variation of the H-component of the geometric field from two equatorial electrojet stations, Huancayo and Addis Ababa, and one non-equatorial electrojet station, Alibag, were studied to find out the trend of solar quiet variation of H for the year 2008. The dH amplitudes of the electrojet stations showed enhancement in H, while there was no enhancement in the non-electrojet station which was located far away from the dip equator. The day-to-day monthly diurnal variation was, however, observed in all the three stations. Also, at nighttime, the dH amplitudes of all the stations were non-zero which we attributed to non-ionospheric current sources like the magnetosphere since at night there was no solar radiations. For seasonal variations, an Equinoctial maximum, J-Solstitial maximum, and S-Solstitial maximum were observed in the equatorial stations while the non-equatorial station recorded an equinoctial minimum, J-solstitial minimum and D-Solstitial minimum.

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5

Stening, Robert J. "Modeling the equatorial electrojet." Journal of Geophysical Research 90, A2 (1985): 1705. http://dx.doi.org/10.1029/ja090ia02p01705.

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6

Akiyama, T., A. Yoshikawa, A. Fujimoto, and T. Uozumi. "Relationship between plasma bubble and ionospheric current, equatorial electrojet, and equatorial counter electrojet." Journal of Physics: Conference Series 1152 (January 2019): 012022. http://dx.doi.org/10.1088/1742-6596/1152/1/012022.

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7

Abdu, M. A. "The international equatorial electrojet year." Eos, Transactions American Geophysical Union 73, no. 5 (1992): 49. http://dx.doi.org/10.1029/91eo00044.

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8

Rastogi, R. G. "Critical problems of equatorial electrojet." Advances in Space Research 12, no. 6 (1992): 13–21. http://dx.doi.org/10.1016/0273-1177(92)90035-v.

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9

Stening, R. J. "What drives the equatorial electrojet?" Journal of Atmospheric and Terrestrial Physics 57, no. 10 (August 1995): 1117–28. http://dx.doi.org/10.1016/0021-9169(94)00127-a.

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10

Kobea, A. T., C. Amory-Mazaudier, J. M. Do, H. Lühr, E. Houngninou, J. Vassal, E. Blanc, and J. J. Curto. "Equatorial electrojet as part of the global circuit: a case-study from the IEEY." Annales Geophysicae 16, no. 6 (June 30, 1998): 698–710. http://dx.doi.org/10.1007/s00585-998-0698-1.

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Abstract. Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they affect the normal eastward Sq field. This paper presents an analysis of ground magnetic field and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY) experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground field and ionospheric electrodynamic data leads to the identification of a sensitive response of the equatorial electrojet (EEJ) to large-scale auroral return current: this response consists in a change of the eastward electric field during the pre-sunrise hours (0400-0600 UT) coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the time-interval 0800-0950 UT. Subsequent to the change in h'F during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA) caused by the high-latitude penetrating electric field. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The ∆H variations observed at the equator are the sum of the following components: SR, DP, DR, DCF and DT.Keywords. Equatorial electrojet · Magnetosphere-ionosphere interactions · Electric fields and currents · Auroral ionosphere · Ionospheric disturbances

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11

Bolaji, Olawale, Oluwafisayo Owolabi, Elijah Falayi, Emmanuel Jimoh, Afolabi Kotoye, Olumide Odeyemi, Babatunde Rabiu, et al. "Observations of equatorial ionization anomaly over Africa and Middle East during a year of deep minimum." Annales Geophysicae 35, no. 1 (January 20, 2017): 123–32. http://dx.doi.org/10.5194/angeo-35-123-2017.

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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.

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12

Rastogi, R. G. "Morphological aspects of a new type of counter electrojet event." Annales Geophysicae 17, no. 2 (February 28, 1999): 210–19. http://dx.doi.org/10.1007/s00585-999-0210-6.

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Abstract. The study describes the time and space morphologies of a rather new type of counter electrojet event on the basis of data from the excellent chain of magnetic and ionospheric observatories along the Indo-Russian longitude sector. Abnormally large westward currents are observed during almost the whole of the daytime hours on a series of days. These events do not form any vortices in the current system and do not apparently seem to be associated with tidal effects or any solar magnetosphere events or geomagnetic disturbances. The existence of a westward electric field over the equatorial ionosphere has been confirmed by the absence of an equatorial type of sporadic E in the ionograms at Thumba precisely during the periods when ∆H at Trivandrum minus ∆H at Alibag is negative. The equatorial F region anomaly was also absent on the counter electrojet day. Such counter electrojet events during the northern winter months of low solar activity years are suggested to be the result of the modified wind system in the ionosphere associated with stratospheric warming events.Key words. Geomagnetism and paleomagnetism (time variations · diurnal to secular) · Ionosphere (electric fields and currents; equatorial ionosphere)

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13

Manju, G., T. K. Pant, C. V. Devasia, S. Ravindran, and R. Sridharan. "Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 – a case study." Annales Geophysicae 27, no. 10 (October 9, 2009): 3853–60. http://dx.doi.org/10.5194/angeo-27-3853-2009.

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Abstract. The electrodynamic effects on the low-mid latitude ionospheric region have been investigated using GPS (global positioning system) data, ionosonde data and ΔH values, during the very large solar flare (X17.2/4B) of 28 October 2003. The results bring out the flare induced unusual behaviour of the equatorial ionosphere on this day just prior to sunset. The important observations are i) Large and prolonged Ne enhancements observed from ionosonde data just after the flare-related peak enhancement in EUV flux. The observed enhancement in Ne is due to the increase in ionization production due to the enhanced EUV flux and the persistence of the enhancement is probably due to the prompt penetration related upliftment of the F layer (just prior to the flare peak phase) to higher altitudes, where recombination rates are lower. ii) A significant enhancement in total electron content (TEC) (~10 TEC units) at regions around the Equatorial Ionization Anomaly (EIA) crest region (Ahmedabad) during the flare in association with the flare related EUV flux enhancement. iii) Similar enhancements seen at stations of Jodhpur and Delhi in the mid latitude sector. iv)The flare related flux enhancements in different longitude sectors in the equatorial electrojet region have been shown to produce positive and negative variations in electrojet strength indicating the presence of current systems having positive and negative polarities in different longitude sectors. Thus the flare effect reveals the longitudinal variation of the counter electrojet events in the Equatorial Electrojet (EEJ) region.

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14

Doumouya, V., and Y. Cohen. "Improving and testing the empirical equatorial electrojet model with CHAMP satellite data." Annales Geophysicae 22, no. 9 (September 23, 2004): 3323–33. http://dx.doi.org/10.5194/angeo-22-3323-2004.

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Abstract. The longitudinal variation of the Equatorial Electrojet (EEJ) intensity has been revised including data from the equatorial station of Baclieu (Vietnam), where an unexpected enhancement of the EEJ magnetic effects is observed. The features of this longitudinal variation were also obtained with the CHAMP satellite, except in the Pacific and Atlantic Oceans, where no ground level data points were available.The EEJ magnetic signatures recorded on board the CHAMP satellite have been isolated for 325 passes in different longitude sectors around local noon. The results have been compared with the EEJ magnetic effects computed using the Empirical Equatorial Electrojet Model (3EM) proposed by Doumouya et al. (2003). The modeled EEJ magnetic effects are generally in good agreement with CHAMP observed EEJ magnetic signatures.

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15

Rastogi, R. G., and N. B. Trivedi. "Asymmetries in the equatorial electrojet around N-E Brazil sector." Annales Geophysicae 27, no. 3 (March 12, 2009): 1233–49. http://dx.doi.org/10.5194/angeo-27-1233-2009.

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Abstract. The paper examines the data of geographic northward (X), eastward (Y) and vertical (Z) components of the magnetic field from a dense array of 26 vector magnetometers operated in N-NE Brazil from November 1990 to March 1991. As expected, the daily variation of X showed a minor maximum around 03:00–04:00 LT and a major maximum around 12:00 LT. The daily range of ΔY showed a strong minimum around noon at all stations. The combined ΔY and ΔX indicated the direction of the equatorial electrojet currents to be flowing along 25° north of east at the centre and 20° north of east at the edges of the equatorial electrojet (EEJ) belt. The centre of the EEJ as defined by the zero intercept of the Z versus latitude was found to be near 1.0° S dip latitude. The electrojet current was stronger in the northern half than in the southern half of the electrojet belt. These anomalies are suggested to be due to the abnormal distribution of the mean magnetic field in this region.

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16

Muniz Barreto, L. "The Equatorial Electrojet: A brief review." Geofísica Internacional 31, no. 2 (April 1, 1992): 115–20. http://dx.doi.org/10.22201/igeof.00167169p.1992.31.2.576.

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Se presenta un breve resumen del descubrimiento del electrochorro ecuatorial (EEJ) y la importancia de América del Sur en la investigación del EEJ. Se discuten algunas cuestiones resueltas y no resueltas sobre el EEJ y el "contraelectrochorro" (CEJ) basado en una descripción de posibles peculiaridades del EEJ en Sudamérica. Se resume el trabajo observacional en Brasil y se incluye una versión breve de los programas de investigación del EEJ en Brasil y Perú. También se dan los lineamientos de un posible programa de cooperación latinoamericana sobre los efectos del EEJ durante el eclipse total de Sol del 11 de julio de 1991.

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17

BHARGAVA, B. N. "A note on the equatorial electrojet." MAUSAM 15, no. 1 (March 9, 2022): 98–100. http://dx.doi.org/10.54302/mausam.v15i1.5526.

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18

ONWUMECHILI, C. A. "Satellite measurements of the equatorial electrojet." Journal of geomagnetism and geoelectricity 37, no. 1 (1985): 11–36. http://dx.doi.org/10.5636/jgg.37.11.

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19

ONWUMECHILI, C. A., and P. C. OZOEMENA. "Latitudinal extent of the equatorial electrojet." Journal of geomagnetism and geoelectricity 37, no. 2 (1985): 193–204. http://dx.doi.org/10.5636/jgg.37.193.

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20

Sastry, T. S., and S. V. S. Sarma. "Equatorial Counter-Electrojet and Magnetic Pulsations." Journal of geomagnetism and geoelectricity 49, no. 10 (1997): 1247–51. http://dx.doi.org/10.5636/jgg.49.1247.

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21

Rastogi, R. G. "Electromagnetic induction by the equatorial electrojet." Geophysical Journal International 158, no. 1 (July 2004): 16–31. http://dx.doi.org/10.1111/j.1365-246x.2004.02128.x.

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22

Onwumechili, C. A., and P. C. Ozoemena. "Contours of equatorial electrojet current density." Journal of Atmospheric and Terrestrial Physics 51, no. 3 (March 1989): 163–68. http://dx.doi.org/10.1016/0021-9169(89)90098-6.

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23

Onwumechili, C. A., and P. C. Ozoemena. "Subsolar elevation of the equatorial electrojet." Pure and Applied Geophysics PAGEOPH 131, no. 3 (1989): 509–25. http://dx.doi.org/10.1007/bf00876842.

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24

Rastogi, R. G., H. Chandra, and K. Yumuto. "Equatorial electrojet in east Brazil longitudes." Journal of Earth System Science 119, no. 4 (August 2010): 497–505. http://dx.doi.org/10.1007/s12040-010-0035-4.

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25

Feldstein, Y. I., V. A. Popov, J. A. Cumnock, A. Prigancova, L. G. Blomberg, J. U. Kozyra, B. T. Tsurutani, L. I. Gromova, and A. E. Levitin. "Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals." Annales Geophysicae 24, no. 8 (September 13, 2006): 2243–76. http://dx.doi.org/10.5194/angeo-24-2243-2006.

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Abstract. We investigate variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. Special attention was paid to the complex structure of the electrojets and their interrelationship with diffuse and discrete particle precipitation and field-aligned currents in the dusk sector. During magnetospheric substorms the eastward electrojet (EE) location in the evening sector changes with local time from cusp latitudes (Φ~77°) during early afternoon to latitudes of diffuse auroral precipitation (Φ~65°) equatorward of the auroral oval before midnight. During the main phase of an intense magnetic storm the eastward currents in the noon-early evening sector adjoin to the cusp at Φ~65° and in the pre-midnight sector are located at subauroral latitude Φ~57°. The westward electrojet (WE) is located along the auroral oval from evening through night to the morning sector and adjoins to the polar electrojet (PE) located at cusp latitudes in the dayside sector. The integrated values of the eastward (westward) equivalent ionospheric current during the intense substorm are ~0.5 MA (~1.5 MA), whereas they are 0.7 MA (3.0 MA) during the storm main phase maximum. The latitudes of auroral particle precipitation in the dusk sector are identical with those of both electrojets. The EE in the evening sector is accompanied by particle precipitation mainly from the Alfvén layer but also from the near-Earth part of the central plasma sheet. In the lower-latitude part of the EE the field-aligned currents (FACs) flow into the ionosphere (Region 2 FAC), and at its higher-latitude part the FACs flow out of the ionosphere (Region 1 FAC). During intense disturbances, in addition to the Region 2 FAC and the Region 1 FAC, a Region 3 FAC with the downward current was identified. This FAC is accompanied by diffuse electron precipitation from the plasma sheet boundary layer. Actually, the triple system of FAC is observed in the evening sector and, as a consequence, the WE and the EE overlap. The WE in the evening sector comprises only the high-latitude periphery of the plasma precipitation region and corresponds to the Hall current between the Region 1 FAC and Region 3 FAC. During the September 1998 magnetic storm, two velocity bursts (~2–4 km/s) in the magnetospheric convection were observed at the latitudes of particle precipitation from the central plasma sheet and at subauroral latitudes near the ionospheric trough. These kind of bursts are known as subauroral polarization streams (SAPS). In the evening sector the Alfvén layer equatorial boundary for precipitating ions is located more equatorward than that for electrons. This may favour northward electric field generation between these boundaries and may cause high speed westward ions drift visualized as SAPS. Meanwhile, high speed ion drifts cover a wider range of latitudes than the distance between the equatorward boundaries of ions and electrons precipitation. To summarize the results obtained a new scheme of 3-D currents in the magnetosphere-ionosphere system and a clarified view of interrelated 3-D currents and magnetospheric plasma domains are proposed.

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26

YACOB, A. "The Indian equatorial electrojet in IGY and IQSY." MAUSAM 18, no. 2 (April 30, 2022): 285–88. http://dx.doi.org/10.54302/mausam.v18i2.4453.

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The parameters of the Indian equatorial electrojet are obtained for the months April to August of the solar maximum year, 1958 and the solar minimum year, 1964. The half-width for the two epochs are found to be 297 km and 276 km respectively, showing only a small (change with solar activity. The total peak current intensity for 1958 is 186 A/km and for 1964 it is 97 A/km. The factor by which the normal current intensity is augmented in the electrojet is, however, found to be a little more for 1964 than for 1958.

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27

Le Mouël, J. L., P. Shebalin, and A. Chulliat. "The field of the equatorial electrojet from CHAMP data." Annales Geophysicae 24, no. 2 (March 23, 2006): 515–27. http://dx.doi.org/10.5194/angeo-24-515-2006.

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Abstract. We apply a simple linear transform, the along-track second derivative, to four years of scalar and vectorial data from the CHAMP satellite. This transform, reminiscent of techniques used in the interpretation of aeromagnetic surveys, is applied either to the geocentric spherical components of the field or to its intensity. After averaging in time and space, we first produce a map of the crustal field, then maps of the equatorial electrojet field at all local times and all universal times. The seasonal variation of the electrojet, its evolution with the solar cycle, and the effect of geomagnetic activity are discussed. The variation of the electrojet with longitude, an intriguing feature revealed by satellite data, is described in some detail, and it is shown that this longitude dependance is stable in time. The existence of a counterelectrojet in the morning, everywhere except over the Pacific Ocean, is established. The signatures of closure electric currents and of interhemispheric currents are also evidenced.

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28

Denardini, C. M., M. A. Abdu, H. C. Aveiro, L. C. A. Resende, P. D. S. C. Almeida, Ê. P. A. Olívio, J. H. A. Sobral, and C. M. Wrasse. "Counter electrojet features in the Brazilian sector: simultaneous observation by radar, digital sounder and magnetometers." Annales Geophysicae 27, no. 4 (April 3, 2009): 1593–603. http://dx.doi.org/10.5194/angeo-27-1593-2009.

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Abstract. In the present work we show new results regarding equatorial counter electrojet (CEJ) events in the Brazilian sector, based on the RESCO radar, two set of fluxgate magnetometer systems and a digital sounder. RESCO radar is a 50 MHz backscatter coherent radar installed in 1998 at São Luís (SLZ, 2.33° S, 44.60° W), an equatorial site. The Digital sounder routinely monitors the electron density profile at the radar site. The magnetometer systems are fluxgate-type installed at SLZ and Eusébio (EUS, 03.89° S, 38.44° W). From the difference between the horizontal component of magnetic field at SLZ station and the same component at EUS (EEJ ground strength) several cases of westward morning electrojet and its normal inversion to the eastward equatorial electrojet (EEJ) have been observed. Also, the EEJ ground strength has shown some cases of CEJ events, which been detected with the RESCO radar too. Detection of these events were investigated with respect to their time and height of occurrence, correlation with sporadic E (Es) layers at the same time, and their spectral characteristics as well as the radar echo power intensity.

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29

Vassal, J., M. Menvielle, Y. Cohen, M. Dukhan, V. Doumouya, K. Boka, and O. Fambitakoye. "A study of transient variations in the Earth's electromagnetic field at equatorial electrojet latitudes in western Africa (Mali and the Ivory Coast)." Annales Geophysicae 16, no. 6 (June 30, 1998): 677–97. http://dx.doi.org/10.1007/s00585-998-0677-6.

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Abstract. In the framework of the French-Ivorian participation to the IEEY, a network of 10 electromagnetic stations were installed at African longitudes. The aim of this experiment was twofold: firstly, to study the magnetic signature of the equatorial electrojet on the one hand, and secondly, to characterize the induced electric field variations on the other hand. The first results of the magnetic field investigations were presented by Doumouya and coworkers. Those of the electric field experiment will be discussed in this study. The electromagnetic experiment will be described. The analysis of the electromagnetic transient variations was conducted in accordance with the classical distinction between quiet and disturbed magnetic situations. A morphological analysis of the recordings is given, taking into consideration successively quiet and disturbed magnetic situations, with the results interpreted in terms of the characterization of external and internal sources. Particular attention was paid to the effects of the source characteristics on the induced field of internal origin, and to the bias they may consequently cause to the results of electromagnetic probing of the Earth; the source effect in electromagnetic induction studies. During quiet magnetic situations, our results demonstrated the existence of two different sources. One of these, the SRE source, was responsible for most of the magnetic diurnal variation and corresponded to the well-known magnetic signature of the equatorial electrojet. The other source (the SR*E source) was responsible for most of the electric diurnal variation, and was also likely to be an ionospheric source. Electric and magnetic diurnal variations are therefore related to different ionospheric sources, and interpreting the electric diurnal variation as induced by the magnetic field diurnal variation is not relevant. Furthermore, the magnetotelluric probing of the upper mantle at dip equator latitudes with the electromagnetic diurnal variation is consequently impossible to perform. In the case of irregular variations, the source effect related to the equatorial electrojet is also discussed. A Gaussian model of equatorial electrojet was considered, and apparent resistivities were computed for two models of stratified Earth corresponding to the average resistive structure of the two tectonic provinces crossed by the profile: a sedimentary basin and a cratonic shield. The apparent resistivity curves were found to depend significantly on both the model used and the distance to the center of the electrojet. These numerical results confirm the existence of a daytime source effect related to the equatorial electrojet. Furthermore, we show that the results account for the observed differences between daytime and night-time apparent resistivity curves. In particular, it was shown that electromagnetic probing of the Earth using the classical Cagniard-Tikhonov magnetotelluric method is impossible with daytime recordings made at dip latitude stations.Key words. Electromagnetics (Transient and time do- main) Geomagnetism and paleomagnetism (geomagne- tic induction) Ionosphere (equatorial ionosphere)

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30

Oppenheim, M. "Evidence and effects of a wave-driven nonlinear current in the equatorial electrojet." Annales Geophysicae 15, no. 7 (July 31, 1997): 899–907. http://dx.doi.org/10.1007/s00585-997-0899-z.

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Abstract. Ionospheric two-stream waves and gradient-drift waves nonlinearly drive a large-scale (D.C.) current in the E-region ionosphere. This current flows parallel to, and with a comparable magnitude to, the fundamental Pedersen current. Evidence for the existence and magnitude of wave-driven currents derives from a theoretical understanding of E-region waves, supported by a series of nonlinear 2D simulations of two-stream waves and by data collected by rocket instruments in the equatorial electrojet. Wave-driven currents will modify the large-scale dynamics of the equatorial electrojet during highly active periods. A simple model shows how a wave-driven current appreciably reduces the horizontally flowing electron current of the electrojet. This reduction may account for the observation that type-I radar echoes almost always have a Doppler velocity close to the acoustic speed, and also for the rocket observation that electrojet regions containing gradient-drift waves do not appear also to contain horizontally propagating two-stream waves. Additionally, a simple model of a gradient-drift instability shows that wave-driven currents can cause nonsinusoidal electric fields similar to those measured in situ.

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31

Rastogi, R. G., D. R. K. Rao, S. Alex, B. M. Pathan, and T. S. Sastry. "An intense SFE and SSC event in geomagnetic <i>H</i>, <i>Y</i> and <i>Z</i> fields at the Indian chain of observatories." Annales Geophysicae 15, no. 10 (October 31, 1997): 1301–8. http://dx.doi.org/10.1007/s00585-997-1301-x.

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Abstract. Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent sudden commencement (SSC) of geomagnetic storm at 1518 h on 17 June 1991. The solar flare effects (SFE) registered on the magnetograms appear to be an augmentation of the ionospheric current system existing at the start time of the flare. An equatorial enhancement in ΔH due to SFE is observed to be similar in nature to the latitudinal variation of SQ (H) at low latitude. ΔY registered the largest effect at 3.6° dip latitude at the fringe region of the electrojet. ΔZ had positive amplitudes at the equatorial stations and negative at stations north of Hyderabad. The SSC amplitude in the H component is fairly constant with latitude, whereas the Z component again showed larger positive excursions at stations within the electrojet belt. These results are discussed in terms of possible currents of internal and external origin. The changes in the Y field strongly support the idea that meridional current at an equatorial electrojet station flows in the ionospheric dynamo, E.

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32

Rao, D. R. K., and R. L. Asinkar. "On Ps6 and longer period geomagnetic pulsations in the Indian equatorial region." Annales Geophysicae 12, no. 7 (June 30, 1994): 655–63. http://dx.doi.org/10.1007/s00585-994-0655-6.

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Abstract. Adopting an appropriate procedure suitable for processing the amplitude-time records based on the two-component spectral analysis technique, the statistical information on Ps6 and other longer periods are worked out on the geomagnetic field registrations in the Indian longitudinal regions at and away from the equatorial electrojet influence. The storm interval during 21 and 22 September 1982 has been chosen for the analysis, as violent and regular cyclic variations of the geomagnetic field were recorded in all the three components of the field at the Indian observatories. The procedure, when applied to two intervals of afternoon and night conditions of equatorial ionosphere, showed practically the same polarisation characteristics in the H-D plane at all the frequencies under the equatorial electrojet. At far away places from this influence, the ellipticities are found to be relatively to the west during the afternoon. These, along with the other results, are discussed.

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33

Pallam Raju, D., and R. Sridharan. "High resolution 2-D maps of OI 630.0 nm thermospheric dayglow from equatorial latitudes." Annales Geophysicae 16, no. 8 (August 31, 1998): 997–1006. http://dx.doi.org/10.1007/s00585-998-0997-6.

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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).

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34

Chakrabarty, D., R. Sekar, H. Chandra, R. Narayanan, B. M. Pathan, and K. S. V. Subbarao. "Characterizations of the diurnal shapes of OI 630.0 nm dayglow intensity variations: inferences." Annales Geophysicae 20, no. 11 (November 30, 2002): 1851–55. http://dx.doi.org/10.5194/angeo-20-1851-2002.

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Abstract. Measurements of OI 630.0 nm thermospheric dayglow emission by means of the Dayglow Photometer (DGP) at Mt. Abu (24.6° N, 73.7° E, dip lat 19.09° N), a station under the crest of Equatorial Ionization Anomaly (EIA), reveal day-to-day changes in the shapes of the diurnal profiles of dayglow intensity variations. These shapes have been characterized using the magnetometer data from equatorial and low-latitude stations. Substantial changes have been noticed in the shapes of the dayglow intensity variations between 10:00–15:00 IST (Indian Standard Time) during the days when normal and counter electrojet events are present over the equator. It is found that the width (the time span corresponding to 0.8 times the maximum dayglow intensity) of the diurnal profile has a linear relationship with the integrated electrojet strength. Occasional deviation from this linear relationship is attributed to the presence of substantial mean meridional wind.Key words. Ionosphere (equatorial ionosphere; ionosphere – atmosphere interactions; ionospheric disturbances)

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35

RASTOGI, R. G. "Geomagnetic Disturbance Effects on Equatorial Electrojet Current." Journal of geomagnetism and geoelectricity 44, no. 5 (1992): 317–24. http://dx.doi.org/10.5636/jgg.44.317.

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36

Wang, X. H., and A. Bhattacharjee. "Gradient drift eigenmodes in the equatorial electrojet." Journal of Geophysical Research 99, A7 (1994): 13219. http://dx.doi.org/10.1029/94ja00600.

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37

Rastogi, R. G. "Magnetic storm effects at equatorial electrojet stations." Earth, Planets and Space 58, no. 5 (May 2006): 645–57. http://dx.doi.org/10.1186/bf03351962.

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38

Kudeki, Erhan, Bela G. Fejer, Donald T. Farley, and Christian Hanuise. "The Condor Equatorial Electrojet Campaign: Radar results." Journal of Geophysical Research 92, A12 (1987): 13561. http://dx.doi.org/10.1029/ja092ia12p13561.

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39

Singh, A., and K. D. Cole. "Ion-neutral collisions and the equatorial electrojet." Journal of Atmospheric and Terrestrial Physics 51, no. 11-12 (November 1989): 947–51. http://dx.doi.org/10.1016/0021-9169(89)90010-x.

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40

Bhattacharyya, A. "Electrojet irregularity parameters from daytime equatorial scintillations." Journal of Atmospheric and Terrestrial Physics 57, no. 2 (February 1995): 151–61. http://dx.doi.org/10.1016/0021-9169(93)e0039-c.

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41

Gasperini, F., and J. M. Forbes. "Lunar-solar interactions in the equatorial electrojet." Geophysical Research Letters 41, no. 9 (May 6, 2014): 3026–31. http://dx.doi.org/10.1002/2014gl059294.

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42

Hassan, Ehab, W. Horton, A. I. Smolyakov, D. R. Hatch, and S. K. Litt. "Multiscale equatorial electrojet turbulence:Baseline 2-D model." Journal of Geophysical Research: Space Physics 120, no. 2 (February 2015): 1460–77. http://dx.doi.org/10.1002/2014ja020387.

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43

Rabiu, A. Babatunde, Olanike Olufunmilayo Folarin, Teiji Uozumi, Nurul Shazana Abdul Hamid, and Akimasa Yoshikawa. "Longitudinal variation of equatorial electrojet and the occurrence of its counter electrojet." Annales Geophysicae 35, no. 3 (April 7, 2017): 535–45. http://dx.doi.org/10.5194/angeo-35-535-2017.

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Abstract. We examined the longitudinal variability of the equatorial electrojet (EEJ) and the occurrence of its counter electrojet (CEJ) using the available records of the horizontal component H of the geomagnetic field simultaneously recorded in the year 2009 (mean annual sunspot number Rz = 3.1) along the magnetic equator in the South American, African, and Philippine sectors. Our results indicate that the EEJ undergoes variability from one longitudinal representative station to another, with the strongest EEJ of about 192.5 nT at the South American axis at Huancayo and a minimum peak of 40.7 nT at Ilorin in western Africa. Obtained longitudinal inequality in the EEJ was explicable in terms of the effects of local winds, dynamics of migratory tides, propagating diurnal tide, and meridional winds. The African stations of Ilorin and Addis Ababa registered the greatest % of CEJ occurrence. Huancayo in South America, with the strongest electrojet strength, was found to have the least occurrence of the CEJ. It is suggested that activities that support strong EEJ inhibits the occurrence of the CEJ. Percentage of occurrence of the CEJ varied with seasons across the longitudes. The order of seasonal variation of morning occurrence does not tally with the evening occurrence order at any station. A semiannual equinoctial maximum in percentage of morning occurrence of the CEJ was obtained at Huancayo and Addis Ababa. Only Addis Ababa recorded equal equinoctial maxima in percentage of evening occurrence of the CEJ. The seasonal distribution of the occurrences of the CEJ at different time regimes implies a seasonal variability of causative mechanisms responsible for the occurrence of the CEJ.

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44

Mengistu, Endalkachew, and Tsegaye Kassa. "Temporal characteristics of the Equatorial Electrojet and Counter Electrojet over Ethiopian sector." Advances in Space Research 55, no. 2 (January 2015): 566–75. http://dx.doi.org/10.1016/j.asr.2014.10.031.

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45

GUPTA, BRD. "Night-time 5Cs, 515 and Bays in H at equatorial electrojet stations in India." MAUSAM 18, no. 4 (April 30, 2022): 531–34. http://dx.doi.org/10.54302/mausam.v18i4.4710.

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It is shown that while at Indian electrojet station Annamalainagar some night-time enhancement is seen, at Trivandrum also an electrojet station on the contrary some night-time diminution is seen for all the three phenomena SC, SI and Bay. It is also shown that in Indian zone the mean ratio decreases from north to south while in American zone the mean ratio increases from north to south.

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46

Manju, G., K. S. Viswanathan, and S. Ravindran. "Spatial and temporal variations of small-scale plasma turbulence parameters in the equatorial electrojet: HF and VHF radar observational results." Annales Geophysicae 23, no. 4 (June 3, 2005): 1165–73. http://dx.doi.org/10.5194/angeo-23-1165-2005.

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Abstract. The spatial and temporal variations of various parameters associated with plasma wave turbulence in the equatorial electrojet (EEJ) at the magnetic equatorial location of Trivandrum (8.5° N, 77° E; dip 0.5° N) are studied for the first time, using co-located HF (18MHz) and VHF (54.95MHz) coherent backscatter radar observations (daytime) in the altitude region of 95-110km, mostly on magnetically quiet days. The derived turbulence parameters are the mean electron density irregularity strength (δn/n), anomalous electron collision frequency (νe*) and the corrected east-west electron drift velocity (Vey). The validity of the derived parameters is confirmed using radar data at two different frequencies and comparing with in-situ measurements. The behaviour of δn/n in relation to the backscattered power during weak and strong EEJ conditions is also examined to understand the growth and evolution of turbulence in the electrojet.

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47

Yizengaw, Endawoke, and Brett A. Carter. "Longitudinal, seasonal and solar cycle variation in lunar tide influence on the equatorial electrojet." Annales Geophysicae 35, no. 3 (April 5, 2017): 525–33. http://dx.doi.org/10.5194/angeo-35-525-2017.

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Abstract. It has been well documented that the lunar tidal waves can modulate the ionospheric electrodynamics and create a visible influence on the equatorial electrojet (EEJ). The lunar tide influence gets intensified around noon, primarily during new and full Moon periods. However, the longitudinal, seasonal and solar cycle variability in the lunar tide influence on ionospheric current systems is not well understood yet. In order to investigate this, 17 years (1998–2014) of extensive magnetometer observations at four longitudinal sectors (western American, western and eastern African, and Asian) have been analyzed. All observations performed during magnetically active periods (Kp>3) have been excluded for this study to eliminate storm contributions to the geomagnetic field variation at the geomagnetic equator. This study's quantitative analysis revealed significant longitudinal, seasonal and solar cycle dependence of the lunar tide influence on the equatorial electrojet.

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48

Doumouya, V., J. Vassal, Y. Cohen, O. Fambitakoye, and M. Menvielle. "Equatorial electrojet at African longitudes: first results from magnetic measurements." Annales Geophysicae 16, no. 6 (June 30, 1998): 658–66. http://dx.doi.org/10.1007/s00585-998-0658-9.

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Abstract. In the framework of the French participation in the International Equatorial Electrojet Year (IEEY), ten magnetotelluric stations were installed between November 1992 and November 1994 along a 1200-km-long meridian profile, between Lamto (latitude 6.2°N, Côte d'Ivoire) to the south and Tombouctou (latitude 16.7°N, Mali) to the north. These stations measured digitally the three components of the magnetic field and the two components of the telluric electric field, and operated over a period of 20 months. The magnetic data is used to study the features of the equatorial electrojet (EEJ) in West African longitude. The measurement of the telluric electric field variations will be presented elsewhere. Hourly mean values are used to study the morphological structure of the regular diurnal variation SR of the three components (H, D, and Z) of the earth magnetic field and to characterize the EEJ during magnetically quiet days. The occurrences of the counter-electrojet (CEJ) are set forth, emphasizing its seasonal variability. Assumed to be a current ribbon, the EEJ main parameters (the position of its center, its width, and the amplitude of its current density at the center) are determined. A preliminary analysis of the time variations of these parameters is presented over period of 20 months (from January 1993 to August 1994). Results are compared with those obtained during previous experiments of the same kind.

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Olatunbosun, LG, A. O. Olabode, and EA Ariyibi. "Variability of Equatorial Electrojet (EEJ) at EIA regions." Physics & Astronomy International Journal 6, no. 1 (January 25, 2022): 1–4. http://dx.doi.org/10.15406/paij.2022.06.00241.

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The EEJ is a worldwide solar-driven wind that results in the solar quiet (Sq) current system in the E region of the earth’s ionosphere. The variability of some features such as EEJ, are very important in understanding the complex nature of the ionosphere, especially the low-latitude ionosphere. The magnetometer data from stations located near the equator and outside the edge of the electrojet strip for Africa and India stations were used to estimate and investigate the variability of EEJ in African and Indian Low-Latitudes. The stations are Addis Ababa, Ethiopia (geographic lat/long: 9.03oN/38.76oE) and at Mbour, Senegal for African region (geographic lat/long 14.392oN/343.042oE) and Hyderabad, India (geographic lat/long: 17.413oN/78.555oE) and Beijing Ming Tombs, China for Indian region (geographic lat/long: 40.3oN/116.2oE). The data in XYZ orientation was used to estimate the EEJ strength. The result shows that EEJ exhibits diurnal and seasonal variations and that its variability is stronger in African station than in Indian station, so also is the occurrence of counter electrojet (CEJ).

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Somayajulu, V. V., K. S. Viswanathan, K. S. V. Subbarao, and L. Cherian. "Distortions in the height structure of the equatorial electrojet during counter electrojet events." Journal of Atmospheric and Terrestrial Physics 56, no. 1 (January 1994): 51–58. http://dx.doi.org/10.1016/0021-9169(94)90175-9.

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