脉冲星电层中Diocotron不稳定性的非线性演化：二维PIC模拟
Non-linear evolution of the diocotron instability in a pulsar electrosphere: 2D PIC simulations
摘要：
中子星表面附近的脉冲星磁层物理学仍然没有受到观测的严格限制。然而，人们相信磁层中存在着巨大的真空间隙，非中性等离子体部分填充了中子星周围，形成了电层。在这个电层中的赤道盘是二极管和磁控管不稳定的。为了更好地评估这些不稳定性的长期演变，我们研究了非中性等离子体的行为与粒子模拟的帮助。我们设计了一个二维静电PIC程序。在二极管区，粒子的运动方程服从电漂移近似。等离子体被限制在两个导电壁之间。此外，为了模拟在间隙中的对级联，我们添加了一个源项与带电粒子喂养等离子体。我们考虑了二极管不稳定性的长期非线性演化。我们发现，颗粒往往吸引在一起，形成小涡的高电荷密度旋转的轴的圆柱与只有很小的径向偏移的颗粒。这种颗粒分组在等离子体柱中产生新的低密度或甚至真空间隙。我们表明，粒子注入到等离子体中可以大大增加粒子的扩散整个磁场线。此外，新形成的真空间隙不能通过简单地调用二极管不稳定性来补充。
英文摘要：
(abridged) The physics of the pulsar magnetosphere near the neutron star surface remains poorly constrained by observations. Nevertheless it is believed that large vacuum gaps exist in the magnetosphere, and a non-neutral plasma partially fills the neutron star surroundings to form an electrosphere. The equatorial disk in this electrosphere is diocotron and magnetron unstable. To better assess the long term evolution of these instabilities, we study the behavior of the non-neutral plasma with help on particle simulations. We designed a 2D electrostatic PIC code. In the diocotron regime, the equation of motion for particles obeys the electric drift approximation. The plasma is confined between two conducting walls. Moreover, in order to simulate a pair cascade in the gaps, we add a source term feeding the plasma with charged particles. We consider the long term non-linear evolution of the diocotron instability. We found that particles tend to attract together to form small vortex of high charge density rotating around the axis of the cylinder with only little radial excursion of the particles. This grouping of particles generates new low density or even vacuum gaps in the plasma column. We show that particle injection into the plasma can drastically increase the diffusion of particles across the magnetic field lines. Also, the newly formed vacuum gaps cannot be replenished by simply invoking the diocotron instability.
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