Experinuital Study of Large-Scale Emu Release by Transient and Intermittent Magnetic Reconnection

在TS-3/4装置上，利用两个任意碰撞速度的等离子体环，研究了瞬态和间歇磁场重联的大尺度能量释放。两个大半径为R^-0.2m的等离子体环（TS-3）在外部加速线圈提供的压缩力的帮助下在轴向方向上碰撞并合并在一起。磁场重联首先将重联磁场的磁能通过流出能最终转化为热能，使等离子体β增加30- 50%。新的发现是，即使电流片的有效电阻率与经典的一样低，磁场重联的瞬态效应也会导致快速的合并速度和高功率加热。它们的加热能量随着重联速度的增加而显著增加，这是由于重联流出导致的。等离子体碰撞（入流）速度从0变化到阿尔芬速度V_A的30%， 关于我们 压缩线圈/ PF线圈电流。当入流速度小于0.05 V_A时，等离子体入流流量与出流流量达到平衡，表现出与MRX实验类似的准稳态重联（dB/dt^- dn/dt^-0）。当入流速度超过0.1- 0.2VA时，在重联早期，入流通量超过出流通量，导致电流片中等离子体和磁通量明显堆积。当入流速度增加到0.2VA以上时，在重联后期出现两种快速重联机制。当回旋半径pi较大时，快速入流将片宽δ压缩到小于pi，导致有效电流片电阻率和重联速度异常增大。一个问题是，如果快速流入过压缩有效电阻率η与经典电流片一样低的电流片，则流入速度如何增加<cl>。当δ&gt;&gt;p_i保持η^-η_<cl>时，流入磁通在电流片周围堆积，导致电流片的快速增长和峰值。当磁通堆积超过临界极限时，板从被挤压的X点区域被机械地弹出。在通量堆积期间，重联速度相对较慢，而在抛射期间则急剧加快，这与日冕观测结果一致。发现片材弹出发生两次或三次。如果我们将初始重联通量增加到足够大。这些事实表明，在低电阻率条件下（pi &lt;&lt;δ），等离子体流入通量大于等离子体流出通量使准稳态重联由瞬态重联转变为间歇重联。结果表明，电流片的生长和喷射都增加了等离子体的流入量（重联速度），这分别是由于电流片的质量积累和喷射。基于这些结果，电流片的瞬态整形效应的结论，使重联（和流出）更快，即使薄层电阻率保持为经典的低。少

The large-scale energy release of transient and intermittent magnetic reconnection has been studied in the TS-3/4 device using two merging plasma toroids with arbitrary colliding speeds. Two plasma toroids with major radii R^-0.2m (TS-3) were collided and merged together in the axial direction by the help of compression force provided by external acceleration coils. The magnetic reconnection transformed the magnetic energy of reconnecting magnetic field first through the outflow energy finally to the thermal energy, increasing the plasma beta up to 30-50%, A new finding is that the transient effect of magnetic reconnection causes the fast merging speed as well as the high-power heating, even if effective resistivity of the current sheet is as low as classical. Their heating energy increases significantly with their reconnection speed, because the heating is cased by the reconnection outflow. The plasma colliding (inflow) speed was varied from zero to 30% of the Alfven speed V_A using c … More ompression coil/ PF coil currents. When the inflow speed was slower than 0.05 V_A, the plasma inflow flux balanced with the outflow flux, indicating the quasi-steady reconnection (dB/dt^- dn/dt^-0) like the MRX experiment. When the inflow speed exceeded 0.1-0.2V_A, the inflow flux exceeded the outflow flux in the early reconnection phase, causing clear pileup of plasma and magnetic flux in the current sheet. When the inflow speed was increased over 0.2V_A, two types of fast reconnection mechanisms were observed to appear in the late reconnection phase. When the gyro-radius p_i was relatively large, the fast inflow compressed the sheet width δ shorter than p_i, causing the anomalous increase in the effective current sheet resistivity and the reconnection speed. A question is how the inflow speed increases if the fast inflow over-compresses the current sheet whose effective resistivity η is as low as the classical one η_<cl>. When the condition : δ>>p_i maintained η^-η_<cl>, the inflow flux was observed to pileup around the current sheet, causing the rapid growth and peaking of the current sheet. When the flux pileup exceeded the critical limit, the sheet was ejected mechanically from the squeezed X-point area. The reconnection speed was relatively slow during the flux-pileup and became drastically fast during the ejection, in agreement with the solar corona observations. The sheet ejection was found to occur twice or three times. if we increases the initial reconnecting flux sufficiently large. These facts indicate that the plasma inflow fluxes larger than the plasma outflow fluxes transformed the quasi-steady reconnection though the transient one, finally to the intermittent one under the low resistivity condition (p_i<<δ). It is concluded that the growth and ejection of current sheet both increase plasma inflow (reconnection speed) due to its mass accumulation and ejection, respectively. Based on these results, the transient shaping effect of current sheet is concluded to makes the reconnection (and outflow) faster, even if the sheet resistivity stays as low as the classical one. Less