Evidence of short spatial variability of the equatorial electrojet at close longitudinal separation

Chandrasekhar, N.; Arora, Kusumita; Nagarajan, N.

doi:10.1186/1880-5981-66-110

Cited by 13 publications

(25 citation statements)

References 58 publications

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“…It has been established earlier that the eastward electric field ( E region) at equator shows a four‐wave longitudinal structure with a crest at 100°E and a trough at 60°E longitude, attributed to DE3 nonmigrating tide (Lühr et al, ). Similar trend was noted in comparison of CBY and VEN and EEJ and CEJ strengths (Chandrasekhar et al, , , )(from 93–77°). Additionally, using a year's concurrent data with MNC (72°), the westward decrease in EEJ strength as well as increase strength of westward currents demonstrated in a separate analysis (Archana R. K., personal communication, June 25, 2018).…”

Section: Discussionsupporting

confidence: 85%

Effect of Disturbance Electric Fields on Equatorial Electrojet Over Indian Longitudes

et al. 2018

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Prompt penetration (PP) and ionospheric disturbance dynamo (Ddyn) are two expressions of the disturbed electric field developed during a geomagnetic storm in the Earth's ionosphere. Earlier investigations treated these two processes independently over longitudinal separation beyond 20°. In the present study, we investigate the conjunction of these phenomena on equatorial electrojet at 20° longitude separations using daytime magnetic field data from three equatorial sites viz., Minicoy, Vencode, and Campbell Bay and three low‐latitude sites viz., Alibag, Hyderabad, and Nabagram, located within 20° longitude over Indian region, during three intense storms (Dst <− 150 nT). We propose a statistical method to identify PP signatures from large data set. In addition, we distinguish the signatures of PP and Ddyn during early recovery phase of intense storms and compute pure Ddyn signature in the late recovery phase. It is seen that the effect of PP is similar at the three equatorial sites for each storm. We find that signatures of Ddyn are amplified at Minicoy and Vencode compared to Campbell Bay, and their magnitude decreases toward low‐latitude stations, also reflected in the current vector patterns. Our investigations of intense geomagnetic storms show that PP effect dominates the main phase, followed by a combined effect of PP and Ddyn in the early recovery phase. Eventually the Ddyn signature dominates in the late recovery phase with decreasing amplitudes of Ddyn with increasing time. Such investigations can provide new information about variations in ionospheric parameters.

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Section: Discussionsupporting

confidence: 85%

Effect of Disturbance Electric Fields on Equatorial Electrojet Over Indian Longitudes

et al. 2018

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“…Using Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIE‐GCM) model, Doumbia et al [] discussed the contributions of migrating diurnal and semidiurnal tides for the occurrence of counter electrojet phenomena, amplitude, and its longitudinal dependence. As shown in an earlier paper [ Chandrasekhar et al, ], a large number of CEJ events in February 2012 have affected the monthly average. The equinoctial asymmetry in the EEJ strengths during the two equinoxes (i.e., spring and autumn) is also evident in Figures c and d.…”

Section: Discussionmentioning

confidence: 92%

“…Earlier works showed the significant influence of tidal winds on the variability in the EEJ strength [ Le Mouel et al, ; Luhr et al, , , ; Hausler et al, ]. An overview of past studies on longitudinal variability of EEJ is given in Chandrasekhar et al [2014, and references therein].…”

Section: Introductionmentioning

confidence: 99%

Characterization of seasonal and longitudinal variability of EEJ in the Indian region

2014

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This paper presents the seasonal and longitudinal variability of the equatorial electrojet (EEJ) based on geomagnetic variation data from two electrojet stations in the northern Indian Ocean at a longitudinal separation of~15°: i.e., at 77°E and at 93°E. One complete year of data is used (i.e., from November 2011 to October 2012) at the two longitudes and compared with the climatological model of the equatorial electrojet (EEJM-2.0). The results of our analysis show that (i) the monthly averaged hourly values of EEJ strength at 77°E and 93°E are overall in agreement with global characteristics of EEJ with significant departures over the year of study, (ii) the monthly average hourly daytime values at Campbell Bay and Vencode show poor correlation (r < 0.7) for 5 out of 10 months, (iii) comparison of observed EEJ strength at respective longitudes and the current densities derived from EEJM-2.0 show overall agreement with significant differences for monthly mean hourly daytime values at respective longitudes, and (iv) day-to-day variability in noontime EEJ amplitudes between the two longitudes is >10 nT, >20 nT for 30% of quiet days, sorted by planetary index (Kp) <1 and <2. This variability is reflected in monthly average values (V) mechanisms for persistent differences in EEJ on day-to-day basis are sought from perturbation of westward ion drifts by neutral winds caused by the upward propagation of gravity waves from troposphere/stratosphere into the mesosphere. These mechanisms have been identified theoretically and experimentally. The four-wave structure of ionospheric current densities obtained by EEJM-2.0 and other contemporary models closely resembles atmospheric tidal signatures and has a common origin. The magnitude and persistence of these differences, at short spatial scales (15°), are significant observation. These effects are reflected in the monthly and seasonal signatures of EEJ and contribute to the contemporary models.

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“…This also suggests that occurrence of scintillation is consistent with the enhancement of EEJ. A typical diurnal profile for EEJ shows a peak strength of EEJ at time of approximately noon (i.e., Chandrasekhar et al (2014)). In this manner, Alken and Maus (2007) proposed an empirical model of EEJ climatological mean and day-to-day variability as a function of longitude, local time, season, and solar flux.…”

Section: Characteristics Of Daytime Ghz Scintillation In the Vicinitymentioning

confidence: 99%

Daytime gigahertz scintillations near magnetic equator: relationship to blanketing sporadic E and gradient-drift instability

et al. 2015

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Observations made in non-equatorial regions appear to support the hypothesis that the daytime scintillation of radio signals at gigahertz (GHz) frequencies is produced by the gradient-drift instability (GDI) in the presence of a blanketing sporadic E (E sb ) layer. However, the only evidence offered, thus far, to validate this notion, has been some observations of E sb in the vicinity of GHz scintillations. A more comprehensive evaluation requires information about electric field, together with the presence of a steep gradient, which is presumed to be that of E sb . In this regard, the region in the vicinity of the equatorial electrojet (EEJ) appears to be an ideal "laboratory" to conduct such experiments. The dominant driver of electron drift there is the same as that of the EEJ, the vertical polarization electric field, and indications are that the presence of E sb in that vicinity is controlled by a balance in horizontal transport of E sb , between the EEJ electric field and the neutral wind, as described in a model by Tsunoda (On blanketing sporadic E and polarization effects near the equatorial electrojet, 2008). In this paper, we present, for the first time, results from a comprehensive study of daytime GHz scintillations near the magnetic equator. The properties, derived from measurements, are shown, for the first time, to be consistent with a scenario in which E sb presence is dictated by the Tsunoda model, and the plasma-density irregularities responsible for GHz scintillations appear to be produced by the GDI.

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Evidence of short spatial variability of the equatorial electrojet at close longitudinal separation

Cited by 13 publications

References 58 publications

Effect of Disturbance Electric Fields on Equatorial Electrojet Over Indian Longitudes

Effect of Disturbance Electric Fields on Equatorial Electrojet Over Indian Longitudes

Characterization of seasonal and longitudinal variability of EEJ in the Indian region

Daytime gigahertz scintillations near magnetic equator: relationship to blanketing sporadic E and gradient-drift instability

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