Study of Physics of Magnetic Reconnection in Laboratory and Space Plasmas

M. Yamada

Princeton Plasma Physics Laboratory
Princeton University
Princeton New Jersey 08543

It has been recognized that "physics-issue-dedicated" laboratory experiments can contribute significantly to the understanding of the fundamental physics for space-astrophysical plasma phenomena since they can create fundamental physics processes in controlled manner and provide well-correlated measurements at multiple locations simultaneously. This paper reviews the most recent findings on the local physics of magnetic reconnection in the laboratory plasmas as well as in space.
Major results are:
(1) Verification of Hall effects were made in both laboratory and space plasmas
(2) Identification of the electron diffusion region in both laboratory and space plasmas
(3) It was found that the shape of the reconnection layer changes drastically as collisionality of plasma is varied. In a highly collisional plasma, a rectangular shape Sweet-Parker reconnection layer was identified. In the collision-free regime, the shape of the reconnection layer changes to a Petschek-like double edge with much larger reconnection rate.
(4) It was found both in experiments and numerical simulations that the reconnection rate depends on merging angle of field lines [effect of guide field], with the guide field slowing down the reconnection rate.
(5) Electrostatic and electromagnetic fluctuations are observed in the neutral sheets of both laboratory and space plasmas, with notable similarities in their characteristics and their theoretical interpretation. In a laboratory experiment, a correlation was found between the reconnection rate and the amplitude of EM waves.

Finally we report observation of MRX scaling in which reconnection rate is found to increase rapidly as the ratio of the electron mean free path to the scale length increases.

In collaboration with Y. Ren, H. Ji, and S. Gerhardt.