Avino F, Fasoli A, Furno I, Ricci P, Theiler C
Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland.
Phys Rev Lett. 2016 Mar 11;116(10):105001. doi: 10.1103/PhysRevLett.116.105001. Epub 2016 Mar 9.
Plasma blob dynamics on the high-field side in the proximity of a magnetic field null (X point) is investigated in TORPEX. A significant acceleration of the blobs towards the X point is observed. Close to the X point the blobs break apart. The E×B drifts associated with the blobs are measured, isolating the background drift component from the fluctuating contribution of the blob internal potential dipole. The time evolution of the latter is consistent with the fast blob dynamics. An analytical model based on charge conservation is derived for the potential dipole, including ion polarization, diamagnetic, and parallel currents. In the vicinity of the X point, a crucial role in determining the blob motion is played by the decrease of the poloidal magnetic field intensity. This variation increases the connection length that short circuits the potential dipole of the blob. Good quantitative agreement is found between the model and the experimental data in the initial accelerating phase of the blob dynamics.
在TORPEX装置中研究了靠近磁场零点（X点）的高场侧等离子体团块动力学。观察到团块朝着X点有显著加速。在靠近X点处，团块会分裂。测量了与团块相关的E×B漂移，将背景漂移分量与团块内部势偶极子的波动贡献区分开来。后者的时间演化与快速团块动力学一致。基于电荷守恒为势偶极子推导了一个分析模型，包括离子极化、抗磁电流和平行电流。在X点附近，极向磁场强度的降低在决定团块运动方面起着关键作用。这种变化增加了使团块势偶极子短路的连接长度。在团块动力学的初始加速阶段，模型与实验数据之间发现了良好的定量一致性。
