Spatial and temporal distributions of ionospheric currents in subsolar elevations

Onwumechili, C. Agodi

doi:10.1016/s1364-6826(97)00021-7

Cited by 9 publications

(10 citation statements)

References 14 publications

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“…The study shows that the meridional component of the EEJ current intensity evidenced at the Kodaikanal and Annamalainagar stations is an integral part of the zonal component at Trivandrum. This confirms the results of Rastogi (1996) and validates those of Onwumechili (1997). The results suggest that ionospheric conductivity mainly controls the magnitude, while the electric field and ultimately winds mainly control the phase and randomness of the day‐to‐day variability of the hourly amplitudes of Sq .…”

supporting

confidence: 91%

“…Onwumechili (1997) has obtained the current vortices of the EEJ and W Sq from the 1986 observational data of the Indian stations. He gave the electric fields that drive the various components of the EEJ vortex.…”

Section: Discussionmentioning

confidence: 99%

“…This new result is, however, in accord with two recent papers. Onwumechili (1997) has produced the current vortex of the EEJ. It shows that the north–south component of the EEJ current is maximum at the latitude of its focus, at about 3° dip latitude.…”

Section: Temporal Variation Ofday‐to‐day Variability Of Hourly Amplmentioning

confidence: 99%

“…The magnitude of the day‐to‐day variability in D due to the EEJ shown in Table 4 is, surprisingly, much larger than expected from an eastward current. The relatively large D arises from the north–south component of the EEJ current vortex (Onwumechili 1997) as explained in the last paragraph of Section 3.1. The 0 from the north‐south EEJ current has actually been observed at Kodaikanal and Annamalainagar (Rastogi 1996).…”

Section: Temporal Variation Ofday‐to‐day Variability Of Hourly Amplmentioning

confidence: 99%

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Day-to-day variability of geomagnetic hourly amplitudes at low latitudes

Okeke

Onwumechili

Rabiu

1998

Geophysical Journal International

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A study of the variability of the amplitude of Sq at a fixed hour from one day to the next at nine stations from the dip equator to about 22° north of it has produced interesting results. The amplitude and sign of the variability change virtually randomly, making the mean practically zero. The variability occurs at all hours of the day. Its magnitudes in the components D, H and Z have the same diurnal variation, which peaks in the noon period like Sq(H) in low latitudes, and a weak seasonal variation that peaks at the June solstice (local summer). It is demonstrated that changes in the current intensities of the equatorial electrojet (EEJ) and the worldwide part of the Sq (W Sq) current layers have contrasting phases and can sometimes be in antiphase. Indeed, the changes are mostly independent. Inclusion of the magnetic element D revealed that the EEJ current system has not only an east–west but also a north–south component. The study shows that the meridional component of the EEJ current intensity evidenced at the Kodaikanal and Annamalainagar stations is an integral part of the zonal component at Trivandrum. This confirms the results of Rastogi (1996) and validates those of Onwumechili (1997). The results suggest that ionospheric conductivity mainly controls the magnitude, while the electric field and ultimately winds mainly control the phase and randomness of the day‐to‐day variability of the hourly amplitudes of Sq. The random component is attributed to local and/or regional atmospheric winds, probably of gravity wave origin.

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supporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Temporal Variation Ofday‐to‐day Variability Of Hourly Amplmentioning

confidence: 99%

Section: Temporal Variation Ofday‐to‐day Variability Of Hourly Amplmentioning

confidence: 99%

See 2 more Smart Citations

Day-to-day variability of geomagnetic hourly amplitudes at low latitudes

Okeke

Onwumechili

Rabiu

1998

Geophysical Journal International

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“…See text for explanation current vortex invasion from one hemisphere to another, as stated by Mayaud (1967). The observed D variation might also correspond to the existence of a most local ionospheric source as suggested by Vassal et al (1998) and recently deduced from the study of the return current of the equatorial electrojet using the POGO data (Onwumechili, 1997).…”

Section: Current Systems Related To the Observed S R Of H Z And D supporting

confidence: 62%

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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Equatorial electrojet at African longitudes: first results from magnetic measurements

Doumouya

Vassal²,

Cohen³

et al. 1998

Ann. Geophys.

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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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Spatial and temporal distributions of ionospheric currents in subsolar elevations

Cited by 9 publications

References 14 publications

Day-to-day variability of geomagnetic hourly amplitudes at low latitudes

Day-to-day variability of geomagnetic hourly amplitudes at low latitudes

Equatorial electrojet at African longitudes: first results from magnetic measurements

Equatorial electrojet at African longitudes: first results from magnetic measurements

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