New evidence of a meridional current system in the equatorial ionosphere

Maeda, Hiroshi; Iwamoto, Toshihiko; Araki, Tohru; Kamei, T.

doi:10.1029/gl009i004p00337

Cited by 101 publications

(62 citation statements)

References 5 publications

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“…In fact RICHMOND et al (1976) show that (1, -2)* winds, which are derived from the (1, -2) winds by considering the ion drag effect, generate more realistic Sq currents, especially the eastward currents extending to the dusk side at low latitudes. Also, the meridional current system in the equatorial F-region has been detected on the dusk-side (MAEDA et al, 1982). This current system has a clear solar activity dependence.…”

Section: Discussionmentioning

confidence: 83%

Equatorial electrojet strengths in the Indian and American sectors. Part II. During high solar activity.

Patil

Rao

Rastogi

1990

J. geomagn. geoelec

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Strengths of the equatorial electrojets are derived at Indian and American sectors employing the same procedure as in Part I, for high solar activity years. On examining the morphological features of the strengths at this activity including the counter electrojet events, a comparative study is made with these results and those obtained for low solar activity years. It is noticed that the strengths in the American sector are uniformly larger during high solar activity when compared with low activity years. Similar increase at high over low is within the theoretically derived ratio at the Indian sector. Probable reasons for this enhanced ratio at American sector are discussed.Morning counter electrojet events are found to be larger in number in both the sectors during high solar activity years. However, afternoon counter electrojet phenomenon is confined to low solar activity years and is more prominent in the Indian sector. The simultaneous occurrence of counter electrojet intervals at both the sectors in the two phases of solar activity show that the morning simultaneous events are more during high and afternoon events more in low solar activity years. Lunar influence appears to exist in the occurrence of morning counter electrojet which maximises at the lunar ages 05 and 17 at both phases of solar activity.

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Section: Discussionmentioning

confidence: 83%

Equatorial electrojet strengths in the Indian and American sectors. Part II. During high solar activity.

Patil

Rao

Rastogi

1990

J. geomagn. geoelec

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“…According to its morphological shape, this variation could be related to the background planetary Sq current system. The D variation found in MAGSAT dusk data near the dip-equator was interpreted by Maeda et al (1982) as the eect of two meridional currents¯owing in the meridian plane, northward in the northern hemisphere and southward in the southern hemisphere. This ®eld has the same latitudinal structure as the IEEY afternoon D variation, negative to the north and positive to the south.…”

Section: Resultsmentioning

confidence: 99%

“…Nevertheless, the EEJ signature is clearly observed on the data, although weak because of the local times (6 and 18 h) of the orbits. Maeda et al (1982) demonstrated that the D component at dusk was changing with latitude, suggesting the existence of a meridional current associated with the EEJ. The signature of this current was not at all observed at dawn.…”

Section: Spatial Measurementsmentioning

confidence: 99%

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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“…Both of the meridional current system models of Untiedt (1967) and Richmond (1973) yielded more realistic solutions than those of the r uu model. The existence of the meridional current system was evidenced by the observations by rocket measurements (Musmann and Seiler, 1978) and MAGSAT (Maeda et al, 1982). By making a three-dimensional calculation in the equatorial region, Forbes and Lindzen (1976a, b) showed that the equatorial electrojet strength is nearly doubled and the jet region is widened.…”

Section: Basic Conditionsmentioning

confidence: 94%

Numerical analysis of global ionospheric current system including the effect of equatorial enhancement

Tsunomura¹

1999

Ann Geophysicae

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Abstract. A modeling method is proposed to derive a two-dimensional ionospheric layer conductivity, which is appropriate to obtain a realistic solution of the polar-originating ionospheric current system including equatorial enhancement. The model can be obtained by modifying the conventional, thin shell conductivity model. It is shown that the modi®cation for one of the non-diagonal terms (S hu ) in the conductivity tensor near the equatorial region is very important; the term in¯uences the pro®le of the ionospheric electric ®eld around the equator drastically. The proposed model can reproduce well the results representing the observed electric and magnetic ®eld signatures of geomagnetic sudden commencement. The new model is applied to two factors concerning polar-originating ionospheric current systems. First, the latitudinal pro®le of the DP2 amplitude in the daytime is examined, changing the canceling rate for the dawnto-dusk electric ®eld by the region 2 ®eld-aligned current. It is shown that the equatorial enhancement would not appear when the ratio of the total amount of the region 2 ®eld-aligned current to that of region 1 exceeds 0.5. Second, the north-south asymmetry of the magnetic ®elds in the summer solstice condition of the ionospheric conductivity is examined by calculating the global ionospheric current system covering both hemispheres simultaneously. It is shown that the positive relationship between the magnitudes of high latitude magnetic ®elds and the conductivity is clearly seen if a voltage generator is given as the source, while the relationship is vague or even reversed for a current generator. The new model, based on the International Reference Ionosphere (IRI) model, can be applied to further investigations in the quantitative analysis of the magnetosphere-ionosphere coupling problems.

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New evidence of a meridional current system in the equatorial ionosphere

Cited by 101 publications

References 5 publications

Equatorial electrojet strengths in the Indian and American sectors. Part II. During high solar activity.

Equatorial electrojet strengths in the Indian and American sectors. Part II. During high solar activity.

Equatorial electrojet at African longitudes: first results from magnetic measurements

Numerical analysis of global ionospheric current system including the effect of equatorial enhancement

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