THE STUDY OF LONGITUDINAL AND LATITUDINAL VARIATION OF EQUATORIAL ELECTROJET SIGNATURE AT STATIONS WITHIN THE 96°MM AND 210°MM AFRICAN AND ASIAN SECTORS RESPECTIVELY UNDER QUIET CONDITION
ABSTRACT
Solar quiet current ( ) and Equatorial Electrojet (EEJ) are two current systems which are produced by electric current in the ionosphere. The enhancement of the horizontal magnetic field is the EEJ. This research is needed for monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. This study presents the longitudinal and latitudinal variation of equatorial electrojet signature at stations within the 96° 210° African and Asian sectors respectively during quiet condition. Data fromeleven observatories were used for this study. The aim of this study is to investigate the equatorial variation of the solar quite ( ) current, as well as determine the longitudinal and latitudinal magnetic signatures on the EEJ at some African and Asian sectors under quiet condition. The objectives of the study therefore are to: Determine the longitudinal and latitudinal geomagnetic field variations during solar quiet conditions along the 96° 210° ; Investigate monthly variation and diurnal transient seasonal variation; Measure the strength of the EEJ at stations within the same longitudinal sectors of 96° 210° ; and find out the factors responsible for the longitudinal and latitudinal variation of EEJ under solar quiet condition. Horizontal ( ) component of geomagnetic field for the year 2008 from Magnetic Data Acquisition System (MAGDAS) network were used for the study. The International Quiet Days (IQDs) were used to identify quiet days. Daily baseline values for each of the geomagnetic element , can be obtained from 0 = 1⁄2 ( 24 + 1) where 0 is the dailybaseline. The daily baseline was subtracted from the hourly values to get the hourly departure from midnight for a particular day = − 0 where = 1 24 gives the measure of the hourly amplitude of the variation of . The monthly average of the diurnal variation was found. The seasonal variation of was found by averaging the monthly means for Lloyd’s season. Results showed that: The longitudinal and latitudinal variation in the differs in magnitude from one station to another within the same longitude due to the difference in the influence of the EEJ on them, which depends on how far from or near (latitudinal difference) they are to the EEJ band (confined within ±3°) wherein the EEJ current flows eastwards; The highest monthly longitudinal variation of EEJ is 92 at DAV and TIR during September equinox. This high amplitude at DAV andTIR compared with the other 9 stations, showed the presence of higher electric current (equatorial electrojet) in the ionosphere flowing over DAV and TIR. Thus the high magnitude could possibly be due to a greater width of the electrojet over thestations. The variation pattern for daily, monthly and seasonal variation were found to be similar; The magnitude of EEJ strength at stations within the same specified longitude differ where the EEJ strength at ILR is maximum with of 55 at about 1100 LT and maximum EEJ strength at DAV is 93 at about 1200LTwhich is the highest for the specified year; The possible factors responsible for the variation of EEJ is seen to be the ionospheric processes and physical structure such as wind and conductivity. The value peaks between 1000LT and 0200 LT for all the plots and varies with longitude and with latitude. The EEJ value for equinoctial months is seen to be higher than those of solstice months where the buildup flank is steeper in the morning hours than in the evening hours.
