磁约束球马克的倾斜不稳定性
Tilting Instability of Magnetically Confined Spheromaks
摘要：
我们认为倾斜不稳定性的磁约束spheromak使用三维MHD和相对论PIC计算与应用天体物理等离子体，特别是那些发生在磁星磁层。这种不稳定性是由球马克的内禀磁偶极子与外部磁场的反向排列驱动的。最初，球标旋转-倾斜-试图降低其磁势能。结果，在球马克的内部磁场和约束场之间形成电流片。磁重联开始发生;这导致球标新反向排列的磁通量的湮灭。这发生在几个阿尔文时间尺度。在高阶（二阶）球斑的情况下，内核首先被推出包层，导致形成两个几乎独立的倾斜球斑。因此，磁性扭曲的外壳不能稳定内芯。在耗散过程中，扭转阿尔文波带走了初始球马克的螺旋度，违反了泰勒松弛定理的假设。在磁星的巨型耀斑的应用中，倾斜不稳定性的快速发展，以及高阶球斑的不稳定性，使得被捕获的球斑不太可能是持续数百秒的尾辐射的原因。
英文摘要：
We consider the tilting instability of a magnetically confined spheromak using 3D MHD and relativistic PIC calculations with an application to astrophysical plasmas, specifically those occurring in magnetar magnetospheres. The instability is driven by the counter alignment of the spheromak's intrinsic magnetic dipole with the external magnetic field. Initially the spheromak rotates - tilts - trying to lower its magnetic potential energy. As a result a current sheet forms between the internal magnetic field of a spheromak and the confining field. Magnetic reconnection sets in; this leads to the annihilation of the newly counter-aligned magnetic flux of the spheromak. This occurs on few Alfvén time scales. In the case of higher order (second order) spheromak, the internal core is first pushed out of the envelope, resulting in formation of two nearly independent tilting spheromaks. Thus, the magnetically twisted outer shell cannot stabilize the inner core. During dissipation, helicity of the initial spheromak is carried away by torsional Alfvén waves, violating the assumptions of the Taylor relaxation theorem. In applications to magnetars' giant flares, fast development of tilting instabilities, and no stabilization of the higher order spheromaks, make it unlikely that trapped spheromaks are responsible for the tail emission lasting hundreds of seconds.
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