The relationship between the current and the width of the equatorial electrojet

Onwumechili, C. Agodi; Agu, C.E

doi:10.1016/0021-9169(81)90119-7

Cited by 16 publications

(9 citation statements)

References 21 publications

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“…That is, occurrence frequencies displayed morning and afternoon maxima and minima around local noon at Chimbote (3.5°N dip latitude), Chiclayo (5°N dip latitude), and Talara (6.5°N dip latitude) in the American sector. This relationship has been noted by others in ground magnetometer data [ Onwumechili and Ogbuehi , 1967] and in POGO satellite magnetic data [ Onwumechili and Agu , 1981; Ozoemena and Onwumechili , 1988]. Onwumechili and Agu [1981], for example, performed a regression analysis on POGO satellite magnetometer data to show that there is an inverse linear dependence between EEJ width and intensity.…”

Section: Discussionsupporting

confidence: 60%

“…This relationship has been noted by others in ground magnetometer data [ Onwumechili and Ogbuehi , 1967] and in POGO satellite magnetic data [ Onwumechili and Agu , 1981; Ozoemena and Onwumechili , 1988]. Onwumechili and Agu [1981], for example, performed a regression analysis on POGO satellite magnetometer data to show that there is an inverse linear dependence between EEJ width and intensity. A similar behavior in E sq was noted over Kwajalein (4.3°N dip latitude) in the Pacific sector by Tsunoda [1994] and over Fortaleza when the dip latitude reached about 3.6° dip latitude by Abdu et al [1996].…”

Section: Discussionsupporting

confidence: 60%

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On blanketing sporadic E and polarization effects near the equatorial electrojet

Tsunoda

2008

J. Geophys. Res.

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[1] A number of puzzling features have been observed that occur during the day in the vicinity of the equatorial electrojet (EEJ). They include (1) an equatorial belt, essentially collocated with the EEJ, that is virtually devoid of blanketing sporadic E (E sb ); (2) appearances of E sb within that ''forbidden'' belt but only when the EEJ is weak or reversed (i.e., a counterelectrojet); (3) occasional appearances of a secondary current layer above the EEJ; and (4) observations at 4.3°N dip latitude of a latitudinal tilt in the bottomside E layer on one occasion and an unexpectedly large electron drift velocity on another. These features are shown to be accountable if the usual framework for electrodynamics in this region is modified to include the following: (1) transport of E sb that is controlled by a shear in the neutral wind with a crucial contribution from the polarization electric field of the EEJ; (2) the formation of an equatorward boundary for E sb by a dynamical balance between the neutral wind and the polarization electric field; (3) a buildup in conductivity within a band-like region, just poleward of the E sb boundary, from an accumulation of metallic ions; and (4) the appearance of a secondary polarization electric field across the band of enhanced conductivity and current flow throughout the region pervaded by that secondary electric field.

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Section: Discussionsupporting

confidence: 60%

Section: Discussionsupporting

confidence: 60%

On blanketing sporadic E and polarization effects near the equatorial electrojet

Tsunoda

2008

J. Geophys. Res.

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“…The above result is in complete agreement with our earlier results that the width (Onwumechili & Agu 1981a) and other landmark distances (Onwumechili ef al. & 1989) of the equatorial electrojet decrease as its intensity increases.…”

Section: The Relationship Between Current Intensity and Thickness Of supporting

confidence: 94%

“…The increase of the peak current density needed to decrease the half thickness, p km, by unit amount is greater for a small half thickness than for a large half thickness; about 2 A km-2 per km for a half thickness of about 5.4 km, but about 1 A kmP2 per km for a half thickness of about 6.04 km. In this case, actual in situ measurements have fully confirmed results from model fittings by Onwumechili & Ogbuehi (1967), Onwumechili & Agu (1981a) and Onwumechili et al (1989). However, this is the first time the resulting contraction of the electrojet has been demonstrated with a vertical dimension of the electrojet.…”

Section: Discussionsupporting

confidence: 72%

A study of rocket measurements of ionospheric currents-III. Ionospheric currents at the magnetic dip equator

Onwumechili

1992

Geophysical Journal International

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The 31 daytime rocket flight results within 0" or 2" dip latitude provide a good study of several issues leading to the following findings. In this zone, 60 per cent or more of ionospheric current systems have two layers. The lower layer has a peak density of 7 f 4 A k m -' at an altitude of 1 0 6 f 2 k m , a half thickness at half peak of 5.7 f 0.7 km and an altitude extent of 34 f 9 km. The upper layer has a peak density of about 1 A km-' at an altitude of 136 f 8 km and an altitude extent of 19 f 5 km. In some altitude structures, the single layer system is like a hybrid of the lower and the upper layers. The thickness of the equatorial electrojet decreases as its peak current density increases. From this and earlier findings, the electrojet contracts vertically and latitudinally as its peak current density increases. From the sample examined, there is not much difference between the intensities of the lower layers over India and Peru. However, the intensity of the upper layer over India is only about half of its intensity over Peru. The decrease of the electrojet current density in the afternoon is related more to the decrease in the east-west electrostatic field than to electron density or conductivity. A C electric field fluctuations caused by the cross-field instability have been observed in situ in the east-west direction only, in the frequency range of 5 to 120 Hz at altitudes of 85 to 105 km. It is shown that the geometrical and current density structures of the electrojet substantially influence the ratios of its internal to external magnetic field components, all of which initially increase in magnitude with dip distance. Within 0" to 2" dip latitude the ratios are 0.28 f 0.08 for the northward component X, -0.17 f 0.2 for the vertical component 2, and 0.23 f 0.02 for the total field F. A proposed simple measure of day-to-day variability shows promise.

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“…Many studies have investigated the EEJ through measurements in space using low-Earth orbiting satellites and sounding rockets (e.g., Cain and Sweeney, 1973;Onwumechili and Agu, 1981;Onwumechili, 1992;Jadhav et al, 2002;Ivers et al, 2003;Lü hr et al, 2004;Lü hr and Maus, 2006), or on the ground with magnetometer arrays (see review by Forbes, 1981, also Doumouya et al, 1998;Rastogi et al, 2004;Manoj et al, 2006). Theoretical and empirical models have been built to examine physical features and understand large-scale spatial variation in the EEJ (e.g., Sugiura and Cain, 1966;Richmond, 1973;Doumouya et al, 2003;Doumouya and Cohen, 2004;Klimenko et al, 2007;Alken and Maus, 2007).…”

Section: Introductionmentioning

confidence: 99%

Model simulation of the equatorial electrojet in the Peruvian and Philippine sectors

Fang

Richmond

Liu

et al. 2008

Journal of Atmospheric and Solar-Terrestrial Physics

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The relationship between the current and the width of the equatorial electrojet

Cited by 16 publications

References 21 publications

On blanketing sporadic E and polarization effects near the equatorial electrojet

On blanketing sporadic E and polarization effects near the equatorial electrojet

A study of rocket measurements of ionospheric currents-III. Ionospheric currents at the magnetic dip equator

Model simulation of the equatorial electrojet in the Peruvian and Philippine sectors

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