Abstract
For four geomagnetic storms of middle intensity the relationship between the low-latitude magnetic field asymmetry using ASY indices and the intensity of the auroral eastward and westward electrojet was considered. It was asked whether there exists a connection between ASY and the eastward electrojet. To answer this question equivalent current systems were estimated in mid-latitudes. It was found that the observations obviously show no correlative relationship between the low-latitude magnetic-field asymmetry and the eastward electrojet, whereas one exists between ASY and the westward electrojet. To explain the generally accepted common three-dimensional current system between the partial ring current and the eastward electrojet, a condensor model of the three-dimensional current system was developed. It could be shown that the short periodic variations of the partial ring current are shielded by the condensor and cannot influence the eastward-electrojet current.
Highlights
Since the work of Kamide and Fukushima (1972) it has been generally accepted that in the evening sector the asymmetric ring current is part of a three-dimensional current system containing the eastward auroral electrojet
The essential question to be answered by this investigation is the following: Is there a relationship between the low-latitude magnetic ®eld asymmetry and the smallscale equivalent current system in mid-latitudes? The magnetic-®eld observations of the four storms shown in Figs. 1±12 will provide us with the answer
Looking to 0900 and 1100 UT we see at these moments an overlapping of the eastward electrojet by a poleward westward electrojet
Summary
Since the work of Kamide and Fukushima (1972) it has been generally accepted that in the evening sector the asymmetric ring current is part of a three-dimensional current system containing the eastward auroral electrojet. For this reason we deal in this paper with an analysis of the relationship between the storm-time asymmetry and substorm equivalent current system. We will show this using examples in the afternoon/evening sector in midand auroral latitudes for various storms For all these investigations we have to consider that the lowlatitude magnetic-®eld asymmetry cannot be explained alone by an asymmetric ring current; this has been shown by Harel et al (1981) and Crooker and Siscoe (1981). This means that the observed asymmetry of the low-latitude magnetic ®eld during the recovery phase is mainly caused by the local-time dierences of the ring-current decay It will be the task of this work to investigate the relationship between the low-latitude ®eld asymmetry and the mid-latitude current system
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