Particle Acceleration in electrically non-neutral magnetic neutral sheet and application in high energy astrophysics

以往对磁中性片及其粒子凝聚的研究主要集中在电性准中性等离子体的情况下。在这项研究中，考虑了电非中性的情况。我们试图阐明电非中性电流片中粒子加速的机制。这项研究可能会解决长期存在的所谓的西格玛问题。我们利用一种新发展的粒子格子方案(在2009年日本天文学会年会上提出)，在Y点处的磁中性片中发现了准周期磁重联。这种耗散可以解释脉冲星观测到的费米伽马射线望远镜产生的伽马射线稀薄现象。此外，我们还研究了可能由同步加速器耗散和俯仰角散射引起的X射线数据。特别是，我们复制了硬X射线图像，它显示了双峰图像。我们发现，如果高能粒子以小俯仰角的粒子为主，那么观测结果重现得很好。这与激波后等离子体的标准认识相矛盾，首次证明了磁重联在脉冲星风的终止激波中占据了主导地位，说明相对论离心风中并不产生动能主风。因此，西格玛问题是无法解决的。相反，我们认为激波中的磁重联将动能转换为热能，这样就不存在西格玛问题，即风不是由整体运动中的等离子体动能主导的。

Previous study on the magnetic neutral sheet and the particle asscerelation in it has been on cases for electric quasi-neutral plasma. In this study electrically non-neutral cases have been considered. We attempted to clarify the mechanism of particle acceleration in electrically non-neutral current sheet. This study may resole long standing so called sigma-problem.We have found quasi-periodic magnetic reconnection in the magnetic neutral sheet at the Y-point by using a newly developed particle-in-cell scheme (presented at annual meeting of astronomical society of Japan in 2009). This dissipation may explain the gamma-ray raridation from the pulsars observed Fermi gamma-ray telescope.In addition to this, we examine the X-ray data which may caused by synchrotron dissipation and pitch angle scattering. In particular, we have reproduced the hard X-ray image which showd double peaked image. We find that if high energy particles are dominated by ones with small pitch angles, then observation is reproduced well. This contradicts with the standard understanding of the post shock plasma.It is shown for the first time that the magnetic reconnection takes palace in the termination shock of the pulsar wind.It is suggested that the kinetic energy dominant wind is not produced in the relativistic centrifugal wind. Therefore, the sigma-problem cannot be resolved. We rather suggest that the magnetic reconnection in the shock convert the kinetic energy to thermal one so that there is no sigma-problem, i.e., the wind is not dominated by the plasma kinetic energy in bulk motion.