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中子星星（脉冲星）。脉冲星会发出一种称为“脉冲星风”的等离子体的相对速度外流，它将能量传递给星云。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，并在星云内部的终端激波处消散。我们试图证明这张图片是不正确的，实际上风能是电磁的，以给出蟹状星云的新图片。在这个为期三年的项目中，我们已经证明：（1）星云磁场是强烈无序的，（2）通过开发一个偏振模型并与观测结果进行比较，我们证实磁场是强烈无序的，（3）通过X射线和光学望远镜的详细观测，星云流显示出电磁活动。（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耗散。所有这些结果都支持了脉冲星风是由磁能主导的观点，并且在冲击时和冲击后通过例如磁重联的磁能耗散导致了星云发射。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.