Kinetic structure of reconnection layers in the magnetosphere and associated ion transport

Two-dimensional (2-D) hybrid simulations are carried out to study the reconnection structure at the magnetopause and in the magnetotail with the presence of a finite guide magnetic field (By ≠ 0) and a magnetosheath shear flow. Ion velocity distribution in the reconnection layer is investigated. Also ion transmission and reflection at the reconnection layer is examined by tracing orbits of individual particles.; For symmetric cases with By = 0, as in the plasma sheet of the magnetotail, two pairs of slow shocks are present in the reconnection layer. A temperature anisotropy with T ∥ > T⊥ is found in the transition region of the slow shock. In the asymmetric case with By = 0 an intermediate shock bounds the reconnection layer from the magnetosheath side. A D-shaped ion velocity distribution is present. For asymmetric cases with By ≠ 0 with a shear flow speed DeltaV = 0, as near the subsolar region, a large-amplitude rotational discontinuity is present on the magnetosheath side of the reconnection layer, across which the magnetic field changes direction from the magnetosheath to the magnetosphere. The Walen relation is examined to be nearly satisfied in the rotational discontinuities with lefthand and righthand polarizations.; For a higher-latitude reconnection in the Northern Hemisphere, where a shear flow is present across the magnetopause, the structure of the reconnection layer northward of the X line is very different from that southward. Below the X line, a thin, strong rotational discontinuity is always present on the magnetosheath side. For a certain guide field By (zero or nonzero), field-aligned currents J∥ are generated in the reconnection layer associated with the perturbations in By. The dominant senses of J ∥ above and below the X line, however, remain similar for different shear flow speeds. D-shaped ion distributions are present in cases with northward magnetosheath flows. The neutral X line is developed along the z direction in this case and the convection of the field lines is along y direction.; The reflection (transmission) rate decreases (increases) as beta decreases. In the presence of a shear flow speed DeltaV ≠ 0 the reflection rate above the X line is, in general, smaller than that below the X line. (Abstract shortened by UMI.)...