Abstract
Abstract. The past four decades have seen a considerable amount of research on the study of magnetospheric substorms, and over most of these years the expansive phase of the substorm has been associated with the development of a three dimensional current system that has been termed the substorm current wedge. This current system has been thought to be a consequence of the short-circuiting of crosstail current through the ionosphere, and is viewed as a distinctive current system operating independently from the directly driven current with which it co-exists. The purpose of this paper is to show that the substorm current wedge should be viewed as an equivalent current system rather than a real current system. It will be shown that the magnetic perturbation pattern associated with the current wedge can be modeled as purely a perturbation of the directly driven current system in the midnight sector. Keywords. Magnetospheric physics (Auroral phenomena; Current systems; Magnetotail; Storms and substorms
Highlights
IntroductionAs far back as the beginning of the 20th century, the electric current system associated with the onset and early development of the substorm expansive phase (EP) was thought to be three dimensional, involving a downward field-aligned current (FAC) in the postmidnight sector connected to an upward FAC in the evening sector by an electrojet current flowing westward in the auroral ionosphere (cf Birkeland, 1908)
As far back as the beginning of the 20th century, the electric current system associated with the onset and early development of the substorm expansive phase (EP) was thought to be three dimensional, involving a downward field-aligned current (FAC) in the postmidnight sector connected to an upward FAC in the evening sector by an electrojet current flowing westward in the auroral ionosphere.The evidence for this presumption were the magnetic field perturbations observed at high latitudes during the strong auroral displays that were later termed substorms by Akasofu (1964)
We argue that the equivalent current system that is presently called the substorm current wedge is exactly that – an equivalent current system, rather than a real current system
Summary
As far back as the beginning of the 20th century, the electric current system associated with the onset and early development of the substorm expansive phase (EP) was thought to be three dimensional, involving a downward field-aligned current (FAC) in the postmidnight sector connected to an upward FAC in the evening sector by an electrojet current flowing westward in the auroral ionosphere (cf Birkeland, 1908). The evidence for this presumption were the magnetic field perturbations observed at high latitudes during the strong auroral displays that were later termed substorms by Akasofu (1964). Any discussions of the three dimensional current system associated with that phenomenon are based on magnetometer measurements alone, and the substorm current wedge (as it is called) is still only an equivalent current system, albeit three dimensional in character
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