Experimental Study of 3-D Fast Magnetic Reconnection with Plasma Particle Effects

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The TS-3 merging experiments revealed new features of fast magnetic reconnection : 1) anomalous resistivity of current sheet, 2) fast shock structures, 3) mechanical ejection of current sheet and 4) 3-D localized reconnection. We first developed the axial merging of two tokamak plasmas whose Reynolds number were over 10^3 in the TS-3 merging device. The effective resistivity of the current sheet was found to increase by factor 10-30 when the sheet-width was compressed shorter than the ion gyroradius. This general feature caused the reconnection speed to increase with the external compression force for the current sheet and inversely with the field amplitude Bx parallel to the X-point lines. Our result clearly revealed the dependence of anomalous resistivity on the ion gyroradius in agreement with the recent macroparticle simulation by Horiuchi et al. The fast shock structure was also confirmed for the first time during the tokamak reconnection in agreement with the solar satellite observation by Tsuneta et al. When the resistivity of the current sheet was kept as small as the classical one, the overcompression of the sheet was found to cause the mechanical ejection of current sheet under the high-Bx condition and the 3-D localized reconnection under the low-Bx condition. Both phenomena are the most probable mechanisms for the fast reconnection without anomalous resistivity. Based on those results, we hold "the University of Tokyo Symposium 2000 on Magnetic Reconnection in Space and Laboratory Plasmas" in the university of Tokyo (Feb. 28-Mar. 4) together with 140 reconnection researchers in the field of solar/space and magnetosphere observations, theory/simulations and laboratory experiments. We found for the first time the common physics of fast reconnection and current sheet structures through the inter relationship between those four major fields of reconnection.