Features of Magnetopause Reconnection

        I will discuss two new results from particle-in-cell simulations
of reconnection at the Earth's magnetopause.  In two dimensional
simulations the presence of a guide field (one perpendicular to the
reconnection plane) and a density asymmetry across the current layer
creates a diamagnetic drift that advects the X-line with the electron
diamagnetic velocity.  When the relative drift between the ions and
electrons is of the order the Alfv\'en speed the large scale outflows from
the X-line necessary for fast reconnection cannot develop and the
reconnection is suppressed.
        Three dimensional particle simulations of a system with a guide
field, but no density asymmetry, develop turbulence driven by intense
electron beams forming near the X-line and separatrices. The turbulence
collapses into localized nonlinear structures in which the electron
density is depleted.  The drag produced by these structures is
self-consistently generated and behaves in some senses --- but not all ---
like an anomalous resistivity.
        I will discuss observational evidence for both diamagentic
stabilization and the presence of electron holes at the magnetopause.