Comparison of the POGO satellite and ground measurements of the magnetic field of the equatorial electrojet

Abstract

The magnitude of the equatorial electrojet signature, S, being a measure of its magnetic field at the POGO satellite and normalized to 400 km altitude, is plotted against its contemporaneous corresponding horizontal magnetic field, X, at a station on or very close to the dip equator under the recording satellite. It is found that they correlate very well; that the ratio k of X to S is 2.28±0.53 and is the same in all regions. Because the vertical component, Z, of the field at Ibadan is largely due to the electrojet, we have also compared it with S, resulting in a good value of 2.03 for k. We also computed a theoretical value of k = 2.58 from Onwumechili's three-dimensional model of the electrojet and this value agrees with and buttresses the observed value of k. It is argued that imperfect removal of the worldwide Sq is most likely to be the major cause of the scatter; that peculiarities of crustal and upper mantle conductivity are not likely to wholly account for the scatter nor for any regional differences in the value of k. However, the previously discordant results have been reconciled and regional differences in the values of k are no longer significant.