Energy flow and closure of current systems in the magnetosphere

Abstract

The result of an attempt to express the net energy input to the magnetosphere‐ionosphere system in terms of upstream solar wind parameters is presented. Seven types of electric current system within the magnetosphere are defined and discussed, and it is found that only three of these systematically transfer energy into the magnetosphere from the solar wind. One of these is the magnetotail current system, and the other two form the field‐aligned current observed at the northern edge of the auroral oval. In order to calculate energy input, reasonable models are developed for each of a number of magnetospheric processes. These include (1) flow through the shock, flow in the magnetosheath, and merging; (2) reconnection and the neutral line in the magnetotail; and (3) Alfven layer shielding of the inner magnetosphere from convective flow, nightside pressure balances, and precipitation, and hence from these the width and conductance of the nightside auroral oval. The use of these models permits the development of explicit equations for the total energy input to the magnetosphere‐ionosphere system in terms of upstream solar wind parameters. The interplanetary magnetic field strength and orientation and the solar wind velocity dominate energy input via the nightside plasma sheet. The density of the solar wind is also an important variable for the energy input by the high‐latitude current systems.

Formation of magnetospheric plasma population regimes coupled with the dynamo process in the convection system

“…In the Dungey model this overlapping region must be the dynamo (J.E < 0) for the region-1 FAC system. However, it results in a peculiar current configuration in which same current simultaneously branches to the pure Chapman-Ferraro current and region-1 FAC at the frank magnetopause [Atkinson, 1978, Figure 2]. While J.E < 0 is reasonable for the region-1 FAC system, it is not so reasonable for the pure Chapman-Ferraro current.…”

“…As shown previously, weaker dynamo than that of cusp distributes in wide area of the magnetopause [Tanaka, 1995[Tanaka, , 2000aSiscoe et al, 2000]. In traditional models such as Atkinson [1978] the region-1 FAC system driving the convection is a line-tying current that connects the Chapman-Ferraro current and FAC. To consider this configuration is equivalent to state that the convection is driven directly by the tangential Maxwell stress through the dragging of magnetic field (the Dungey's open model).…”

“…This concept is equivalent to the direct generation of region-1 FAC by tangential Maxwell stress on the magnetopause [Atkinson, 1978;Stern, 1984]. However, the stretching and contraction effects do not fully explain convection inside the magnetosphere that includes incompressible low-b areas in the near-Earth region and in the ionosphere because the response of this system requires a global self-consistency.…”

“…[30] In the current configuration of Atkinson [1978] the line-tying current must overlap on the shoulder of the magnetosphere behind the cusp with the pure ChapmanFerraro current that is connected to the dayside magnetopause. In the Dungey model this overlapping region must be the dynamo (J.E < 0) for the region-1 FAC system.…”

“…To investigate this problem, a self-consistent picture of the convection and FAC is examined as a compound system, strictly considering incompressibility of the inner magnetosphere. Through these studies, a new insight will be given for the dynamo process together with an alternative interpretation for the nature of line-tying current [Atkinson, 1978] that forms the region-1 FAC system to drive the convection.…”