Strongly magnetized pure electron plasmas are characterized by a long-range coulomb interaction without effective shielding and by two-dimensionally (2D) incompressible dynamics equivalent to the 2D Euler fluid. The culmination among the fluid dynamic experiments may be the discovery of crystallized states of vortex strings generated in a nonlinear stage of K-H instability [1]
To appreciate abundant physical significances in the self-organization process, we have carried out a series of experimental investigations by singling out a simplified configuration involved in the vortex crystallization. Our typical configuration consists of a set of discrete distributions of electron clumps initially immersed in a well-defined continuous distribution of background electrons (background vortex = BGV). The first topic here is how the merger of two clumps is accelerated or blocked by different levels of BGV to a degree substantially different from the clumps' dynamics in vacuum. [2] Modifications in the BGV distribution generated by the clumps' motion exert critical effects on the merger or on generation of a closely tied state of the clumps. The second topic is how the unit cell of vortex crystals is established in interaction with other clumps and fragmentary vorticity distributions, remnants of preceding vortical interactions. Here a set of three clumps with different number of electrons (circulations) settle down to the vertices of an equilateral triangle only in the presence of BGV, roughly with a speed increasing with the circulation of BGV.[3] The symmetrization of the unit cell may be analyzed from several points of view. Here we discuss it in terms of cooling of clumps' random motion by fluctuating fields in BGV.

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