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arXiv 1907.09447physics.plasm-ph
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脉冲功率驱动实验中磁化等离子体流的相互作用

Interactions of magnetized plasma flows in pulsed-power driven experiments

L G Suttle, G C Burdiak, C L Cheung, T Clayson, J W D Halliday, J D Hare, S Rusli, D Russell, E Tubman, A Ciardi, N F Loureiro, J Li, A Frank, S V Lebedev

摘要:

磁化等离子体的超音速流是通过将1 MA峰值、500 ns的电流脉冲施加到被称为反向线阵列的平行线的圆柱形布置来产生的。等离子体流由烧蚀的金属丝材料的JxB加速产生,并且由驱动电流在源处嵌入几特斯拉的磁场。该装置已被用于各种实验调查磁化等离子体流的相互作用。在研究磁重联的实验中,携带相反方向的磁场的逆流流的碰撞导致形成重联层,我们观察到离子达到的温度远高于经典加热机制的预测。在等离子体团不稳定性下,该层的破裂取决于流入等离子体的性质,这可以通过选择线阵列材料来控制。在其他实验中,通过在磁化等离子体流的路径上放置障碍物来形成磁化冲击。磁通量在导电障碍物前面的堆积产生作用于离子惯性长度距离处的上游电子的磁性前驱物。该前体随后通过离子-电子流体解耦发展成陡峭的密度转变。具有强的私人磁场的障碍物影响上游流的距离远得多,提供了一个扩展的弓形激波结构。在障碍物周围的区域中,磁压阻挡了流动,形成了等离子体材料的空隙,类似于行星体周围的磁层顶,具有自生磁场。

英文摘要:

A supersonic flow of magnetized plasma is produced by the application of a 1 MA-peak, 500 ns current pulse to a cylindrical arrangement of parallel wires, known as an inverse wire array. The plasma flow is produced by the JxB acceleration of the ablated wire material, and a magnetic field of several Tesla is embedded at source by the driving current. This setup has been used for a variety of experiments investigating the interactions of magnetized plasma flows. In experiments designed to investigate magnetic reconnection, the collision of counter-streaming flows, carrying oppositely directed magnetic fields, leads to the formation of a reconnection layer in which we observe ions reaching temperatures much greater than predicted by classical heating mechanisms. The breakup of this layer under the plasmoid instability is dependent on the properties of the inflowing plasma, which can be controlled by the choice of the wire array material. In other experiments, magnetized shocks were formed by placing obstacles in the path of the magnetized plasma flow. The pile-up of magnetic flux in front of a conducting obstacle produces a magnetic precursor acting on upstream electrons at the distance of the ion inertial length. This precursor subsequently develops into a steep density transition via ion-electron fluid decoupling. Obstacles which possess a strong private magnetic field affect the upstream flow over a much greater distance, providing an extended bow shock structure. In the region surrounding the obstacle the magnetic pressure holds off the flow, forming a void of plasma material, analogous to the magnetopause around planetary bodies with self-generated magnetic fields.

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