Dr. Michael Swisdak
University of Maryland
Breaking magnetic field lines during reconnection
Magnetic reconnection is the driver of explosive releases of energy in the laboratory and nature, including solar and stellar flares and storms in the Earth's magnetosphere. The release of magnetic energy requires a topological change in magnetic geometry: field lines must break and reconnect to release energy. The dissipation mechanism that enables magnetic field lines to break during reconnection has remained a mystery since the first models of reconnection were proposed in the 1950s. Classical resistivity is too small to explain reconnection observations. We explore the dynamics of magnetic reconnection with 3-D particle-in-cell simulations and analytic analysis. The simulations reveal that strong currents and associated high electron-ion streaming velocities that develop near the x-line can drive instabilities. The electron scattering caused by this turbulence produces an enhanced drag, "anomalous resistivity", that has been widely invoked as the dissipation mechanism. We have demonstrated that these electron current layers become strongly turbulent. The surprise, however, is that the turbulence driven by an electron sheared-flow instability completely dominates traditional streaming instabilities and the associated turbulent driven "anomalous viscosity" balances the reconnection electric field and therefore breaks field lines.