Abstract
The interaction between the solar wind and the earth's magnetosphere has been studied by using a time‐dependent three‐dimensional magnetohydrodynamic model in which the interplanetary magnetic field (IMF) pointed in several directions between dawnward and southward. When the IMF is dawnward, the dayside cusp and the tail lobes shift toward the morningside in the northern magnetosphere. The plasma sheet rotates toward the north on the dawnside of the tail and toward the south on the duskside. For an increasing southward IMF component, the plasma sheet becomes thinner and subsequently wavy because of patchy or localized tail reconnection. At the same time the tail field‐aligned currents have a filamentary layered structure. When projected onto the northern polar cap, the filamentary field‐aligned currents are located in the same area as the region 1 currents with a pattern similar to that associated with auroral surges. Magnetic reconnection also occurs on the dayside magnetopause for southward IMF. The steady dayside reconnection mainly occurs in the antiparallel merging region nearest the subsolar point and drives strong convection near the magnetopause as reconnected field lines flow tailward. This causes an enhancement of the polar cap and region 1 field‐aligned currents. The polar cusp field‐aligned currents evolve from the polar cap (NBz) field‐aligned currents as the IMF is rotated from northward to southward.
Published Version
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