Abstract
Abstract. The paper examines the data of geographic northward (X), eastward (Y) and vertical (Z) components of the magnetic field from a dense array of 26 vector magnetometers operated in N-NE Brazil from November 1990 to March 1991. As expected, the daily variation of X showed a minor maximum around 03:00–04:00 LT and a major maximum around 12:00 LT. The daily range of ΔY showed a strong minimum around noon at all stations. The combined ΔY and ΔX indicated the direction of the equatorial electrojet currents to be flowing along 25° north of east at the centre and 20° north of east at the edges of the equatorial electrojet (EEJ) belt. The centre of the EEJ as defined by the zero intercept of the Z versus latitude was found to be near 1.0° S dip latitude. The electrojet current was stronger in the northern half than in the southern half of the electrojet belt. These anomalies are suggested to be due to the abnormal distribution of the mean magnetic field in this region.
Highlights
Background of the present studyFollowing the study by Schuster (1889, 1908) several analyses of the diurnal variation of geomagnetic field have been made
Egedal (1947) showed that when the daily range of H at the equatorial and low latitude stations available are plotted against the magnetic dip at the place, a sharp narrow peak of enhanced range of H is observed over the equator
Combining the large set of ionospheric drift observations, ionospheric sounding results and geomagnetic data at stations close to the dip equator in India, Rastogi (1975) has shown that H observed at electrojet stations are the resultant effect of two currents (1) one always flowing eastward at 106 km and associated with the global Sq current system due to the electric field system generated by the solar-lunar tides; (2) the second current at a lower level of 100 km flowing eastward during normal and westward during partial or full electrojet periods
Summary
Following the study by Schuster (1889, 1908) several analyses of the diurnal variation of geomagnetic field have been made. With the operation of new magnetic stations at equatorial latitudes in different longitudes during the International Geophysical Year (IGY), Rastogi (1962) found that the strength of electrojet 3c0urrent is largest at Huancayo in a region of low background magnetic field intensity and is smallest in Trivandrum a region of high magnetic field. He suggested that the Cowling conductivity may be inversely related to the mean magnetic field intensity. This paper is an attempt to understand the micro scale variations of EEJ in a longitude sector in which the magnetic meridian departs appreciably from the geographic meridian
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