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

TS-3并合实验揭示了快速磁场重联的新特征：1）电流片的异常电阻率，2）快速激波结构，3）电流片的机械弹射，4）三维局域重联。在TS-3托卡马克等离子体轴向合并装置上首次实现了雷诺数大于10^3的两个托卡马克等离子体的轴向合并。电流片的有效电阻率被发现增加了10-30倍时，片宽度被压缩短于离子回旋半径。这一一般特征导致重联速度随着电流片的外部压缩力而增加，并且与平行于X点线的场振幅Bx成反比。我们的结果清楚地揭示了异常电阻率对离子回旋半径的依赖关系，与Horiuchi等人最近的宏观粒子模拟结果一致。在托卡马克重联过程中，也首次证实了快激波结构，与Tsuneta等人的太阳卫星观测结果一致。当电流片的电阻率保持在经典电阻率时，在高Bx条件下，过压缩导致电流片的机械弹出，而在低Bx条件下，则导致三维局域重联.这两种现象都是在没有异常电阻率的情况下快速重联的最可能机制。根据这些结果，我们与太阳/空间和磁层观测、理论/模拟和实验室实验领域的140名重联研究人员一起，在东京大学举行了“2000年东京大学空间和实验室等离子体磁重联研讨会”（2月28日至3月4日）。通过这四个主要重联场之间的相互关系，我们首次发现了快速重联和电流片结构的共同物理机制。

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.