Equatorial Electrojet Current

Onwumechili, C. Agodi

doi:10.1201/9780203756706-3

Cited by 16 publications

(18 citation statements)

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“…The equatorial electrojet (EEJ) and equatorial ionization anomaly (EIA) are prominent daytime effects of the low‐latitude ionospheric phenomena that are driven by the eastward electric field (EEF) (Heelis, ; MacDougall, ). The EEJ (Chapman, ) is one of the unique daytime ionospheric phenomena, defined as an intense eastward current flowing in the form of a ribbon‐shaped band roughly 600 km wide in the E region ionosphere flanking the geomagnetic equator of the Earth (Egedal, ; Forbes, ; Onwumechili, ). The pressure gradients from solar and auroral heating, with additional forcing by tidal energy from below, are possible drivers of the thermospheric neutral winds (Blanc & Richmond, ; Titheridge, ).…”

Section: Introductionmentioning

confidence: 99%

“…The atmospheric wind at ionospheric heights sets a tidal motion current due to differential solar heating in the Northern and Southern Hemisphere that converges at the geomagnetic equator and forms a jet‐like current in the ionosphere. In addition, the special geometry of the geomagnetic field at the equator, together with the nearly perpendicular incidence of solar radiation, causes an equatorial enhancement in the effective conductivity, which then leads to an amplification of the jet current that forms a belt‐like structure flowing eastward during the day along the geomagnetic equator in the E region ionosphere (Baumjohann & Treumann, ; Onwumechili, ), forming the EEJ. This enhanced EEF acts perpendicular to the northward geomagnetic field at equatorial latitudes and lifts up plasma with vertical E × B drift to higher altitudes.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Electric Field and Neutral Wind on the Asymmetry of Equatorial Ionization Anomaly

et al. 2018

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The zonal electric field and the meridional neutral wind are the principal drivers that define the geometry and characteristics of the equatorial ionization anomaly (EIA). Here we present the response of the EIA to the variability of the zonal electric field based on measurements of the equatorial electrojet (EEJ) currents and trans‐equatorial neutral winds for the generation and control of the asymmetries of the EIA crests of total electron content (TEC) in the western side of the South American continent. The EEJ strengths are determined using a pair of magnetometers. The 24‐hr trans‐equatorial neutral wind profile is measured using the Second‐Generation, Optimized, Fabry‐Perot Doppler Imager (SOFDI) located near the geomagnetic equator. The EIA is evaluated using TEC data measured by Global Positioning System (GPS) receivers from the Low‐Latitude Ionospheric Sensor Network and several other networks in South America. A physics‐based numerical model, Low‐Latitude Ionospheric Sector, and SOFDI data are used to study the effects of daytime meridional neutral winds on the consequent evolution of an asymmetry in equatorial TEC anomalies during the afternoon and onward for the first time. We find that the configuration parameters such as strength, shape, amplitude, and latitudinal width of the EIAs are affected by the eastward electric field associated with the EEJ under undisturbed conditions. The asymmetries of EIA crests are observed more frequently during solstices and the September equinox than in the March equinox season. Importantly, this study indicates that the meridional neutral wind plays a very significant role in the development of the EIA asymmetry by transporting the plasma up the field lines. This result suggests that a precise observation of the latitudinal TEC profile at low latitudes can be used to derive the meridional wind.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Electric Field and Neutral Wind on the Asymmetry of Equatorial Ionization Anomaly

et al. 2018

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“…Resulting from this current is an electrostatic field directed east‐west (dawn‐to‐dusk) in the dayside of the ionosphere. At the magnetic dip equator, where the B field is horizontal, this electric field results in an enhanced eastward current within ±3° of the magnetic dip equator, known as the EEJ [ Onwumechili , ; Casey , ].…”

Section: Introductionmentioning

confidence: 99%

Influences of various magnetospheric and ionospheric current systems on geomagnetically induced currents around the world

et al. 2017

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Ground‐based observations of geomagnetic field (B field) are usually a superposition of signatures from different source current systems in the magnetosphere and ionosphere. Fluctuating B fields generate geoelectric fields (E fields), which drive geomagnetically induced currents (GIC) in technological conducting media at the Earth's surface. We introduce a new Fourier integral B field model of east/west directed line current systems over a one‐dimensional multilayered Earth in plane geometry. Derived layered‐Earth profiles, given in the literature, are needed to calculate the surface impedance, and therefore reflection coefficient in the integral. The 2003 Halloween storm measurements were Fourier transformed for B field spectrum Levenberg‐Marquardt least squares inversion over latitude. The inversion modeled strengths of the equatorial electrojets, auroral electrojets, and ring currents were compared to the forward problem computed strength. It is found the optimized and direct results match each other closely and supplement previous established studies about these source currents. Using this model, a data set of current system magnitudes may be used to develop empirical models linking solar wind activity to magnetospheric current systems. In addition, the ground E fields are also calculated directly, which serves as a proxy for computing GIC in conductor‐based networks.

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“…The scanned ionograms (15 min) have been physically scaled to find the peak frequencies of E layer ( f o E s ) and F layer ( f o F peak ) respectively at 16:00 IST daily. The equatorial electrojet is demarcated as a constricted strip (within ±3° of the dip equator) of enriched eastward current streaming during daytime in the elevation region of 100–110 km (Onwumechili, ). This is a part of the purported Sq (Solar quiet) current system in the E region induced by atmospheric winds in the existence of the “Earth's magnetic field” (wind dynamo effects).…”

Section: Experimental Details and Data Analysismentioning

confidence: 99%

Vertical Coupling From the Lower Atmosphere to the Ionosphere: Observations Inferred From Indian MST Radar, GPS Radiosonde, Ionosonde, Magnetometer, OLR (NOAA), and SABER/TIMED Instrument Over Gadanki

et al. 2019

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Simultaneous wind observations from Mesosphere Stratosphere Troposphere (MST) radar collectively with Global Positioning System (GPS) radiosonde over Gadanki, covering altitude range of 3.6–20 km (January–December 2009; 365 days), divulge the propagation of lower atmospheric waves up to the ionosphere. It is combined with temperature data (20–110 km) observed from Sounding of the Atmosphere using the Broadband Emission Radiometry (SABER) instrument onboard Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, ionosonde observations, and daily Outgoing Longwave Radiation (OLR) data acquired from the National Ocean and Atmospheric Administration (NOAA; centered around Gadanki [13.5°N, 79.2°E]) for the same time period. Long‐period oscillations with periodicities of ~64, ~32, and ~21 days are witnessed along with the well‐known oscillations of ~16, ~6.4, and ~5.3 days. Most of the long‐period oscillations are dominantly perceived during the summer months (April–June 2009), which can even exist up to September. These long‐period oscillations are found to propagate from lower tropospheric heights up to ionospheric heights with large vertical wavelengths (~300–400 km, in some cases) near to transition zones of atmospheric layers (e.g., tropopause, stratopause, and mesopause). Signatures of vertical coupling of atmosphere through large vertical wavelengths (indicating possible intraseasonal connections) is clearly observed in the equatorial electrojet current and the peak plasma frequencies of ionospheric layers (E and F regions). Noticeable reduction of the wave oscillations in spatial scale with upsurge in spatial damping is evidently visible, in the tropical stratosphere and mesosphere, which can be attributed to stratospheric ozone.

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Equatorial Electrojet Current

Cited by 16 publications

References 1 publication

Effects of Electric Field and Neutral Wind on the Asymmetry of Equatorial Ionization Anomaly

Effects of Electric Field and Neutral Wind on the Asymmetry of Equatorial Ionization Anomaly

Influences of various magnetospheric and ionospheric current systems on geomagnetically induced currents around the world

Vertical Coupling From the Lower Atmosphere to the Ionosphere: Observations Inferred From Indian MST Radar, GPS Radiosonde, Ionosonde, Magnetometer, OLR (NOAA), and SABER/TIMED Instrument Over Gadanki

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