ION REFLECTION AND TRANSMISSION DURING RECONNECTION AT THE EARTHS SUBSOLAR MAGNETOPAUSE

Composition measurements in an accelerated flow event at the Earth's dayside magnetopause show evidence for reflection and transmission of magnetospheric and magnetosheath ion species. Furthermore, a single velocity transformation approximately tangent to the magnetopause surface orders the individual transmitted and reflected ion distributions on both sides of the magnetopause into field-aligned flow at V(A), the local Alfven speed. These observations provide strong evidence for a kinetic description of magnetic reconnection at the magnetopause.