Abstract
Variations of equatorial electrojet (EEJ) in six Magnetic Data Acquisition System (MAGDAS) stations (four stations within the magnetic equator region and two stations outside the region) on the 210oMagnetic Meridian (MM) chain were examined. Data of hourly values of horizontal component of magnetic field, H in the year 2007 for Cooktown (CKT), Amami-oh-Shima (AMA), Davao (DAV), Langkawi (LKW), Yap- Island (YAP) and Cebu (CEB) were used in the study. The electrojet current was studied using both the estimation method and Fambitakoye simulation model to determine the correlation between their results. The strength of equatorial electrojet in the stations were estimated with respect to Cooktown (CKT; 15.48°N, 145.25°E), a station located outside the electrojet region. The maximum electrojet strength was observed in the month of March in Davao (DAV), Cebu (CEB) and Langkawi (LKW) with values of 107.5, 88.5 and 64.08 nT, respectively. The model simulation of EEJ current presents maximum values of 237.9, 207 and 160 nT in DAV, CEB and LKW, respectively in the same month. This result establishes a similarity in the performance of the methods but with higher values in the model performance. A linear correlation analysis between them showed average correlation coefficient values of 0.81 in Yap-Island (YAP), 0.84 in LKW, 0.6 in DAV and 0.54 in CEB. The data also show variability in EEJ, with results showing higher EEJ current magnitude for stations closer to the dip equator. The Root Mean Square Error (RMSE) was carried out to determine the suitability of the model for in the four seasons for each station. Result shows that the model performed better for March equinox in Cebu (3.58) and Yap-Island (5.97), December solstice (8.96) and September equinox in Davao and Langkawi (6.55), respectively. Key words: Equatorial electrojet, dip equator, magnetic data acquisition system (MAGDAS), Fambitakoye model, E-region, solar quiet.
Highlights
The ionosphere is electrically conducting due to the partly ionized plasma generated by photoionization from solar radiation, which is the major source of solar quiet (Sq) current
The concept and study of Equatorial Electrojet (EEJ) current have been traced to Chapman (1951) who observed that the daily variation of geomagnetic field component at the equatorial stations is due to the superimposition of Sq current and the EEJ current flowing eastward at the mid latitude
EEJ is enhanced by localized ionospheric currents and physical structure flowing at the dip equator with higher current intensities during the daytime, which are responsible for Sq variation
Summary
The ionosphere is electrically conducting due to the partly ionized plasma generated by photoionization from solar radiation, which is the major source of solar quiet (Sq) current. The concept and study of Equatorial Electrojet (EEJ) current have been traced to Chapman (1951) who observed that the daily variation of geomagnetic field component at the equatorial stations is due to the superimposition of Sq current and the EEJ current flowing eastward at the mid latitude. (1973) and Onwumechili (1997) observed that the daily variation of geomagnetic field component at the equatorial station is due to the superimposition of the Sq current and the EEJ current flowing eastward at the lower altitude.
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