Magnetosphere–Ionosphere Convection as a Compound System

Abstract

Convection is the most fundamental process in understanding the structure of geospace and disturbances observed in the magnetosphere-ionosphere (M-I) system. In this paper, a self-consistent configuration of the global convection system is considered under the real topology as a compound system. Investigations are made based on the M-I coupling scheme by analyzing numerical results obtained from magnetohydrodynamic (MHD) simulations which guarantee the self-consistency in the whole system under the Bv (magnetic field and velocity) paradigm. It is emphasized in the M-I coupling scheme that convection and field-aligned current (FAC) are different aspects of same physical process characterizing the open magnetosphere. Special attention is given in this paper to the energy supplying (dynamo) process that drives the FAC system. In the convection system, the dynamo must be constructed from shear motion together with plasma population regimes to steadily drive the convection. Convection patterns observed in the ionosphere are also the manifestation of achievement in global self-consistency. A primary approach to apply these concepts to the study of geospace is to consider how the M-I system adjusts the relative motion between the compressible magnetosphere and the incompressible ionosphere when responding to given solar-wind conditions. The above principle is also applicable for the study of disturbance phenomena such as the substorm as well as for the study of apparently unique processes such as the flux transfer event (FTE), the sudden commencement (SC), and the theta aurora. Finally, an attempt is made to understand the substorm as the extension of enhanced convection under the southward interplanetary magnetic field (IMF) condition.

Magnetosphere‐Ionosphere Convection Under the Due Northward IMF

“…This is the structure consistent with the general theory of the dynamo formation (Tanaka, 2003(Tanaka, , 2007Tanaka et al, 2016). Compared with the structure of magnetic field lines, pressure decreases along the advection of pink and blue** field lines, that is, along stream lines of the reverse cells.…”

Substorm simulation: Insight into the mechanisms of initial brightening

“…As Dynamo (II) steadily exists under the southward IMF [Tanaka, 2007], Dynamo (I) and Dynamo (III) would be most important for the initial brightening. Dynamo (I) is associated with the inner high-pressure region, while the Region 1-sense FAC around the off-equatorial high-pressure region is associated with the outer high-pressure region.…”

Dayside four‐sheet field‐aligned current system during IMF BY‐dominated periods

“…The purpose of this paper is to provide a new view of the dayside four‐sheet FAC system in terms of ionospheric convection. Although the basic idea we present here was already given by Watanabe et al [2004, section 5.3], Tanaka [2007, section 5.3], and Watanabe and Sofko [2008, section 4], in this paper we discuss the issue in more depth with support from observations.…”

“…The magnetosphere is a simple voltage generator and the reconnection voltages are mapped to the ionosphere. Evidently, such a treatment is insufficient for the true understanding of the convection cell formation in the ionosphere, as reviewed by Tanaka [2007]. The M‐I system consists of a region of compressible high‐ β plasma (magnetosphere) and a region of incompressible low‐ β plasma (ionosphere), where the dimensionless parameter β represents the ratio of the plasma thermal pressure to the magnetic pressure.…”