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