Developing a new picture of the Crab Nebula

蟹状星云的中心有一颗快速旋转的强磁性中子星(脉冲星)。脉冲星发出一种相对流出的等离子体，称为“脉冲星风”，将能量传递给星云。根据星云的传统图像，脉冲星风的能量主要以等离子体动能的形式存在，这些动能在星云内部的终止激波时耗散。我们试图证明这幅图是不正确的，而实际上风能是电磁的，从而给出了一幅新的蟹状星云的图景。通过这三年的计划，我们已经证明了(1)星云磁场是强烈无序的，(2)通过建立极化模型并将其与观测结果相比较，我们证实了磁场是强烈无序的，(3)通过使用X射线和光学望远镜的详细观测，星云流动显示了电磁活动，以及(4)我们模拟了激波和磁中性片之间的相互作用，并显示了磁场的有效消散。所有这些结果都支持这样的观点，即脉冲星风是由磁能主导的，激波时和激波后通过磁重联的磁能耗散导致星云发射。然而，我们仍然需要进一步的调查，才能对蟹状星云上发生的事情有一个令人信服的结果。

The Crab Nebula has a rapidly rotating and strongly magnetic neutron star (pulsar) at its center. The pulsar emits a relativisitic outflow of plasmas called "pulsar wind", which conveys energy to the nebula. According to the traditional picture of the nebula, the energy of the pulsar wind is mostly in the form of plasma kinetic energy which dissipates at the termination shock at the inner part of the nebula. We attempt to show that this picture is not correct, and in reality the wind energy is electromagnetic to give a new picture of the Crab Nebula.Throughout this three year project, we have shown that (1) the nebula magnetic field is strongly disordered, (2) by developing a model for polarization and comparing it with observation we confirm that magnetic field is strongly disordered, (3) with detailed observation in use of X-ray and optical telescopes, the nebula flow shows electromagnetic activity, and (4) we model an interaction between shock and magnetic neutral sheets, and show an efficient dissipation of the magnetic field. All these results support the idea that the pulsar wind is dominated by the magnetic energy, and dissipation of magnetic energy at the shock and after the shock through e.g. by magnetic reconnection causes the nebula emission. However, we still need further investigations to have a convincing result for what is going on the Crab Nebula.