New evidence of a meridional current system in the equatorial ionosphere

Abstract

An interesting variation in the geomagnetic D‐component has been found by analysis of the Magsat data. Characteristics of this variation are: that it appears everyday on the low‐latitude duskside and is antisymmetric about the dip equator (negative in the northern hemisphere); that the magnitude (from 5 to 25 nT) depends upon the geographic longitude and altitude; and that no corresponding change can be seen on the ground magnetic data. The change suggests a meridional current system in the equatorial ionosphere, produced in association with the electrojet current along the dip equator. This effect should be taken into account in the study of geomagnetic anomaly of internal origin with the Magsat data.