PHYSICS OF MAGNETOSPHERIC POLAR CAP BY ANALYSIS OF FIELD-ALIGNED CURRENTS.

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I have obtained new knowledge on magnetospheric physics, by analyzing the geomagnetic field data that was acquired with various artificial satellites, which includes the following:1. Large-scale field-aligned current systems associated with northward interplanetary magnetic field (NBZ current system).The NBZ field-aligned currents are thought to flow so as to transfer the sunward plasma stress down to the polar cap ionosphere so that large-scale sunward plasma convection is maintained in the central polar-cap plasma domain. The acquisition of this sunward plasma stress from the interplanetary medium is thought to take place in the magnetospheric high-latitude boundary layer often called the plasma mantle.2. Large-scale Region 1 and Region 2 field-aligned current systems.The region 1 current system is thought to originated in the magnetospheric voltage generator, whereas the region 2 current system is ascribable to the combination of the voltage generator and current generator.3. Large-scale magnetospheric equatorial currents.The electric current flowing parallel to and near the geomagnetic equatorial plane is comprised of an azimuthal current flowing westward and a radial current flowing toward the earth in the evening sector and away from the earth in the morning sector. These horizontal currents exhibit a net positive divergence (source) in the evening sector and a net negative divergence (sink) in the morning sector. The location, flow direction and the intensities of these divergent currents are almost identical with those of the region 2 field-aligned current system. The westward ring current and the region 2 current system are closely connected.4. Substorm-associated field-aligned currents.The three-dimensional current system throughout the course of substorm is not solely ascribable to a diversion of magnetospheric cross-tail current but a development of radial current is essental.