International equatorial electrojet year : the African sector

International audienceThis paper presents the IEEY project in the African sector. The amount of our interpreted data is presently too short to allow proper scientific conclusions. Nevertheless, fist typical results illustrate our network possibilities. Some preliminary observations are briefly pre- , sented for their interest towards immediate research goals

On the complexities of ionospheric current systems equator ward of Sq.current focus

The horizontal magnetic field, SPMF(H), superposed on the monthly mean Sq(H) to compose the diurnal profile of Sq(H) on a given quit day, has been found to be complex. Its complex diurnal pattern varies from day to day and can be different at two stations on the same longitude. However, the pattern has been found to be normally very similar at all the stations in the equatorial electroject (EEJ) zone and very similar at all the stations in the worldwide part of Sq(WSq) zone outside the influence of the EEJ. If the intensities of the EEJ and the WSq current systems vary independently, 9 possible categories of SPMF in the EEJ zone vis-à-vis the WSq zone are expected to occur. All the 9 possible categories have been found and only the one category in which a quiet day is not substantially different from the monthly mean Sq has occurred preferentially. In particular, variations of the intensities of the EEJ and WSq current systems in phase and in antiphase respectively are found to occur with equal frequency. It is therefore concluded that the intensities of the EEJ and WSq current systems vary independently. This explains the results on the lack of correlation between the amplitudes of Sq(H) in the EEJ zone and the WSq zone. The particular types of SPMF that cause abnormal phase quiet days (APQDs) in the EEJ zone and in the WSq zone respectively are also found. It has been known that the APQDs in the EEJ zone are caused by the type of SPMF that arises from counter equatorial electrojet (CEJ) while the APQDs in the WSq zone are caused by SPMF that is generated by the single vortex current, (SVC) system. Therefore the complexities of the diurnal profiles of Sq(H) and SPMF(H), even on a very quiet day after correcting for Dst, are caused by the interactions of the magnetic fields of the following current systems; the EEJ current system periodically modulated by the lunar current system in accordance with lunar phases and occasionally modulated by the CEJ-like current system on the one part; and the WSq current system occasionally modulated by the SVC system on the other part. Keywords: ionospheric currents, superposed magnetic fields, complex changes. (Global Journal of Pure and Applied Sciences: 2002 8(4): 559-573

Spatial and temporal distribution of ionospheric currents-3: latitude- local time and latitude- Longitude across section of Equatorial Electrojet current density and intensity

A comprehensive analysis of the POGO satellites data of 1967 1969 has enabled us to present the daytime means, based on 09 hr to 15 hr, at each of 36 longitudes, and the all-longitude means at each of 7 local time hours, for each of 9 parameters of the equatorial electrojet (EEJ) necessary for the cross sections. The latitude-local time cross sections of EEJ current density and intensity each displays three contour cells. The forward current contour cell peaks at (12h, 00.) and the return current contour cells peak at (12h, 5.130N) and (12h, 5.130S). The latitude-longitude cross sections of EEJ current density and intensity each displays nine contour cells. The three forward current contour cells peat at (00, 1000E), (00, 1900E) and (00, 2900E). The three return current contour cells to the north peak at (5.350N, 1000E), (5,050N, 1900E) and (5.300, 2900E), while the three to peak at (5.350S, 1000), (5.050S, 1900E), while the three to the south peak at (5.350S, 1000E), (5.050S, 1900E) and (5,300S, 290E). The return current spreads thinly over an area of about four times the area of the forward current. Consequently, the ratio of the peak return current density or intensity to the peak forward current density or intensity is only about one quarter. On the average the percentage ratio is 23.25 0.41. Arising from the decrease of EEJ with latitude while at the same time it increases everywhere as the peak current at the magnetic dip equator increases, the cross sections show that the contours extend farther in latitude when the peak current at the dip equator is larger. Key Words: latitude local time, latitude. longitude cross sections, current density, and intensity inonospheric currents. (Global Journal of Pure and Applied Sciences: 2002 8(3): 361-370

Spatial and temporal distribution of ionospheric currents-4: altitude – local time and altitude – longitude cross sections of Equatoriall Electrojet current density

The rare opportunity given by the unprecedented spatial and temporal coverage of POGO satellites data is exploited to present all possible cross sections of equatorial electrojet (EEJ) current in the group of papers. Here the all-longitude means at 7 hours centred on local noon and the daytime means at 36 longitudes, of the vertical distribution parameters of EEJ current density are provided. The altitudelocal time cross section of EEJ current density has one contour cell peaking at (12 h, 106 km) while the altitude-longitude cross section of EEJ current density has three contour cells peaking at (1000E, 106 km), (1900E, 106 km) and (2900E, 106 km). In both cross sections the contour of a given current density extends farther from the altitude of peak current density when the peak current density at the centre of EEJ is larger. This accounts for the wavy nature of the altitude-longitude cross section. Attention is drawn to two rocket measurements that support this phenomenon. The following conclusions are also reached. (a) The continuous distribution of current density model reproduces the altitude distribution parameters of EEJ current density very well, (b) the altitude distribution parameters of EEJ current density in India and Peru are not significantly different and (c) The altitude distribution parameters of EEJ current density from rockets data and from POGO Satellites data are not significantly different and that (d) It is essential to take into account the lack of symmetry between the vertical distributions of EEJ current density below and above the altitude of EEJ peak current density. (Global Journal of Pure and Applied Sciences: 2002 8(3): 389-398

The relationship between the current and the width of the POGO electrojet during the solstices

SIGLEITItal

International Equatorial Electrojet Year: The African Sector

International audienceThis paper presents the IEEY project in the African sector. The amount of our interpreted data is presently too short to allow proper scientific conclusions. Nevertheless, fist typical results illustrate our network possibilities. Some preliminary observations are briefly pre- , sented for their interest towards immediate research goals