A Kinetic Model for Laboratory and Space Observation of Fast Collisionless Magnetic Reconnection

Magnetic reconnection in the collisionless regime is studied on the Versatile Toroidal Facility (VTF). The detailed evolution of the profiles of plasma density, current density, and electrostatic potential at the onset of driven reconnection is reconstructed experimentally. Despite a constant, externally imposed reconnection drive, we show that the reconnection does not proceed in a steady-state manner. The formation and decay of the current is shown to be related to the evolution of the electrostatic potential and the associated ion polarization currents. The size of the diffusion region is inferred from the detailed knowledge of the electrostatic potential, and is shown to scale with the drift orbit width of the electrons insensitive to the ion mass and plasma density [1]. This scaling is consistent with the drift kinetic approach in Ref. [2].