General features of the magnetic field of the equatorial electrojet measured by the POGO satellites

Onwumechili, C. Agodi; Agu, C.E

doi:10.1016/0032-0633(80)90071-9

Cited by 18 publications

(19 citation statements)

References 7 publications

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“…This experiment suggests that the amplitude of the EE over the dip equator between 450 and 800 km altitude may be affected by other sources. Onwumechili and Agu (1980) observed that the amplitude of the EE tends to oscillate with altitude from 400 to 800 km, but they did not elucidate the cause of this variation. This suggests that the linear altitude correction used in this study may not be correct.…”

Section: ) We Repeat the Procedures Outlined In Steps (2) And (3) Nomentioning

confidence: 96%

“…Onwumechili and Agu (1980) found a variation of the EE with the satellite altitude. Doumouya et al (1998) on the data from ground based magnetotelluric stations in Africa.…”

Section: Introductionmentioning

confidence: 92%

“…This inverted V-shaped feature, marked by CAD in panel (a) of Fig. 1, is the characteristic signature of the equatorial electrojet (Onwumechili and Agu, 1980). Following Onwumechili and Agu, the magnitude of the signature is estimated by measuring the length of the line AB in nanotesla (nT).…”

Section: Measurements Of the Ee And Data Analysismentioning

confidence: 98%

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A study of local time and longitudinal variability of the amplitude of the equatorial electrojet observed in POGO satellite data

Kim

King

2014

Earth Planet Sp

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The local time and longitudinal variations of the amplitude of the equatorial electrojet (EE) are investigated using the POGO series satellite data. An iterative normalization scheme is developed to separate the variations of the amplitude of the EE with respect to longitude and local time. The resulting local time variation of the EE compares favorably with observatory based studies; however, the longitudinal variation is not well resolved. The altitude of the satellite is another factor that affects the amplitude of the EE. We use a simple linear scaling of amplitude of the EE with the inverse of the satellite altitude. An experiment including only the satellite passes below 450 km altitude indicates that there may be problems in correcting the data from higher altitudes. The reason behind the discrepancy between the results from the data limited to below 450 km and the full data set is not understood and requires further investigation.

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Section: ) We Repeat the Procedures Outlined In Steps (2) And (3) Nomentioning

confidence: 96%

“…Onwumechili and Agu (1980) found a variation of the EE with the satellite altitude. Doumouya et al (1998) on the data from ground based magnetotelluric stations in Africa.…”

Section: Introductionmentioning

confidence: 92%

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A study of local time and longitudinal variability of the amplitude of the equatorial electrojet observed in POGO satellite data

Kim

King

2014

Earth Planet Sp

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“…Consequently, it allowed the characterization, on a global scale of the eect of the EEJ from altitudes between 400 and 800 km (Cain and Sweeney, 1973). The analysis of these data demonstrated several global characteristics of the EEJ (Onwumechili and Agu, 1980, 1981a, b, 1982: the EEJ axis is very close to the geomagnetic equator, on a global scale; the EEJ parameters (half width w, peak intensity J 0 , total current I ) change with longitude and local time: w is minimum, and J 0 and I maximum at noon.…”

Section: Spatial Measurementsmentioning

confidence: 97%

Equatorial electrojet at African longitudes: first results from magnetic measurements

Doumouya

Vassal²,

Cohen³

et al. 1998

Ann Geophysicae

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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-kmlong meridian pro®le, between Lamto (latitude 6.2°N, CoÃ te 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 ®eld and the two components of the telluric electric ®eld, 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 ®eld variations will be presented elsewhere. Hourly mean values are used to study the morphological structure of the regular diurnal variation S R of the three components (H, D, and Z) of the earth magnetic ®eld 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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“…They found that, contrary to expectations, the strength of the disturbance would sometimes increase with altitude away from the electrojet. Onwumechili and Agu [1980] pursued this investigation and proposed that the current distribution of the electrojet oscillated with altitude in an exponentially decreasing sinusoid with distance from the Earth. The wavelength of this oscillation was estimated to be 180 km.…”

Section: Introductionmentioning

confidence: 99%

Equatorial electrojet from Ørsted scalar magnetic field observations

et al. 2003

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[1] Previous studies of the longitudinal variation of the local noon electrojet have yielded doubtful results either because of the poor data quality or because the local times of equatorial crossings occurred in the early morning or late afternoon. The recent launch of the Ørsted satellite in a near-circular orbit with slow drift in local time of equatorial crossing has provided the opportunity for researchers to study the electrojet more accurately. Most studies remove the main field using a spherical harmonic model and then search the daytime equatorial passes for the distinctive electrojet trough in total intensity. The present study examines the electrojet for two consecutive 6-month periods and consequently two local time ranges. Pure signal processing is used to remove the main field directly. The residuals are binned separately for night and day passes on a 1°by 1°grid to enhance the signal to noise ratio and are bin centered by a least squares fitted linear model to compensate for the variations in satellite altitude. Thereafter, for each period the compensated night and day binned values are subtracted from each other to produce a difference set. Global plots of the subsequently spatially filtered difference sets reveal an almost constant electrojet 1/e half width of 3°, as seen at satellite altitude apart from a region in the western Pacific. There are four maxima in the electrojet amplitude at 0°-30°E, 90°-120°E, 180°-220°E, and 260°-290°E in each local time range.

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General features of the magnetic field of the equatorial electrojet measured by the POGO satellites

Cited by 18 publications

References 7 publications

A study of local time and longitudinal variability of the amplitude of the equatorial electrojet observed in POGO satellite data

A study of local time and longitudinal variability of the amplitude of the equatorial electrojet observed in POGO satellite data

Equatorial electrojet at African longitudes: first results from magnetic measurements

Equatorial electrojet from Ørsted scalar magnetic field observations

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