Libby Tolman

MIT PSFC

Tuesday, April 11, 2017

5:00pm

Sweet-Parker current sheets are unstable to the tearing mode, suggesting they will not form in physical systems. Understanding magnetic reconnection thus requires study of the stability of a current sheet as it forms. Such formation can occur as a result of incompressible flows into and along the sheet. We discuss an analysis of how the growth rate γ of the tearing instability in a forming current sheet depends on this incompressible flow rate, Γ0, where the flow pattern at the center of a sheet with its length along the y-axis is given by u = (−Γ0x, Γ0y). Our linear analysis is valid when Γ0 ≪ γ0, where γ0 is the dominant growth rate without flows, and reveals a slight reduction in tearing mode growth rate and wave vector of the dominant mode. The analysis of the nonlinear regime states that flows slightly increase the growth rate before collapse, and have no effect during collapse.