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M. Yamada, H. Ji (Princeton Plasma Physics Lab., Princeton U.)
Magnetic reconnection plays a crucial role in determining the topology of magnetic fields in solar flares, magnetospheric substorms, and relaxation processes in laboratory plasmas. Many fundamental issues of magnetic reconnection are being investigated in the MRX (Magnetic Reconnection Experiment) device [1], which creates an environment satisfying the criteria for MHD plasmas with well controlled boundary conditions in a nearly two-dimensional geometry. Detailed structures and key plasma parameters of magnetic reconnection have been measured by extensive diagnostics. Major findings of recent MRX experiments are: (1) The observed reconnection rate can be explained by a generalized Sweet-Parker model [2], which incorporates compressibility, downstream pressure, and the effective resistivity; (2) The reconnection speed and the shape of the diffusion region depend on the merging angle of the reconnecting field; (3) Resistivity is greatly enhanced over the classical values in the collisionless regime; (4) The thickness of current sheet is proportional to ion gyro-radius and ion skin-depth. This result can be translated into a constant drift velocity over a wide range of plasma density, and is closely related to the observed resistivity enhancement. Application of these MRX results to solar flares will be discussed along with the detailed analysis and physics interpretations.
\noindent [1] M.~Yamada, H.~Ji {\em et al.}, Phys. Rev. Lett.~78, 3117(1997).\\ [2] H.~Ji, M.~Yamada {\em et al.}, Phys. Rev. Lett.~80, 3256 (1998).
If the author provided an email address or URL for general inquiries, it is a
s follows:
http://w3.pppl.gov/~mrx