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

Abstract

[1] Based on the magnetosphere-ionosphere (M-I) coupling scheme, convection as a compound system is considered including the generation of plasma population regimes in the magnetosphere. In these considerations, primary elements that must be set to a selfconsistent configuration are convection flows in the magnetosphere and the ionosphere, field-aligned current (FAC) systems, ionospheric currents, energy conversion processes, and plasma population regimes. The convection in the M-I coupling system is inextricably associated with the FACs. In the present results, the region-1 and region-2 FACs are driven by rP current inside the magnetosphere through plasma internal energy accumulated in the cusp and plasma sheet, respectively. In this process, mechanisms to drive the region-1 and region-2 FACs are the same two-step process; tangential Maxwell stress on the magnetopause pumps up plasma internal energy inside the magnetosphere, then plasma internal energy drives the FACs. This dynamo can be driven by a steady convection flow which is suitable to project down to the low-b regions. Thus from the magnetohydrodynamic (MHD) force balance controlling the convection, plasma population regimes appear through a requirement to form dynamo in the magnetosphere, showing that plasma population regimes are indispensable to fulfill the self-consistency in the convection system. In the model that the convection is driven directly by the linetying current, the shoulder of the magnetosphere behind the cusp, where the line-tying current is mixed with the pure Chapman-Ferraro current connected to dayside, constructs the dynamo (J.E < 0) for the region-1 FAC. In the present model with negative IMF B z , on the contrary, the Chapman-Ferraro current in this area is not directly connected with the region-1 FAC but connected with the neutral sheet current in the dayside merging region to increase plasma internal energy (J.E > 0) around the cusp. Similarly, tail theta current system acts to increase plasma internal energy in the plasma sheet through the convection. The magnetospheric model derived from this consideration enables a continuous switch over from the confinement state of geomagnetic field in the ChapmanFerraro model to the convection of Dungey model for nonzero IMF B z . In the present convection model, nearly force-free open field lines are extending from the polar cap into the lobes. Based on the convection model proposed in this paper, a suggestion is given for the substorm models in the next decade that they must develop from a modular model to a globally self-consistent model. Citation: Tanaka, T., Formation of magnetospheric plasma population regimes coupled with the dynamo process in the convection system,

Magnetosphere–Ionosphere Convection as a Compound System

“…The advantage of the MHD approach is that with a help of numerical schemes it realizes self-consistent reproduction of convection through the Bv approach. Many new findings were made by this method as will be seen in the following part of this paper (Tanaka 1995(Tanaka , 1999(Tanaka , 2000a(Tanaka , 2000b(Tanaka , 2001(Tanaka , 2003bFujita et al 2003aFujita et al , 2003b.…”

“…Since it does not strictly consider the low-beta area in the ionosphere, it does not confront a strict requirement to fully relate the convection with FAC closure processes in the magnetosphere which are coupled to dynamo and plasma distribution in the magnetosphere. As a consequence, it took an unexpectedly long time before we understood how these currents fit in the overall picture, although people had been aware that FACs play a major role in the magnetosphere dynamics (Iijima 2000;Tanaka 2000aTanaka , 2003b. A crucial barrier for these considerations has been the difficulty of considering the magnetospheric closure process of FACs.…”

“…Due to the incompressible nature of the convection, plasma and magnetic field motions that are distributed from the magnetosphere to the ionosphere must be organized in a circular configuration without a considerable accumulation at all height. It requires the simultaneous consideration of the entire M-I system including the FAC under a proper self-consistency (Tanaka 2003b). As will be shown in the following part of this paper, the convection must associate not only with the FACs and magnetic perturbations but also with the formation of plasma population regimes to cope with the incompressibility of the inner magnetosphere (Tanaka 2003b).…”

“…In these considerations, however, the whole system driving the magnetosphere-ionosphere (M-I) convection were not yet organized in a self-consistent manner. The present paper tries to advance this problem by reconsidering the self-consistent configuration of M-I convection under a realistic topology, including the field-aligned currents (FACs), ionospheric currents, magnetospheric dynamo process, and plasma population regimes in the magnetosphere (Tanaka 2003b), to show that simultaneous plasma penetration into the magnetosphere and resulting plasma regimes are indispensable to establish the self-consistency in the convection system in the solar wind-magnetosphere-ionosphere (S-M-I) interaction process. In this paper, the system that pursues the global self-consistency under a real topology is called a compound system.…”

Pulsed flows at the high-altitude cusp poleward boundary, and associated ionospheric convection and particle signatures, during a Cluster - FAST - SuperDARN- Søndrestrøm conjunction under a southwest IMF

“…The reconnected flux tubes formed by transient reconnection then move tailward and poleward under a combination of magnetic tension forces (j×B) and magnetosheath flow. By the time they reach the downstream side of the cusp, the j×B force has reversed and the reconnected flux tubes are extracting energy from the flow (Tanaka, 2003). At the time when flux erosion events were first seen in HEOS 2 data, at a locale comparable to ours, Haerendel et al (1978) suggested that "entry of magnetosheath plasma should not be restricted to the cusp region but may continue further down the tail or along the early morning or late evening flanks, depending on the initial orientation of the external field.…”