无力条件下的磁陀星扭曲磁场

Twisted magnetic field of magnetar in force-free condition

磁陀星是一类拥有极强磁场的特殊中子星,也是目前人类发现的宇宙中磁场最强的一类天体.由于其磁场足够强,可以对壳层施加足够的应力导致壳层剪切,从而使磁场发生扭曲.磁陀星外部磁层的行为由磁压所主导,等离子体压强可忽略不计,从而静力学平衡关系退化为洛伦兹力为零.本文尝试用无力磁场模型研究磁陀星磁场的扭曲,包括求解磁陀星外部磁场的变量分离的流函数解,给出磁感线的数值模拟结果以及磁感线偏转角、磁能的数值计算.

Magnetars are a type of neutron stars with extremely powerful magnetic fields,which also have the strongest magnetic fields in the universe ever discovered by human.The magnetic field of a magnetar has not only a poloidal component.Because of its high intensity,it can apply enough stress on the shell of the star to cause shear,which leads to the twist of the magnetic field around the stellar surface.Magnetars fit the force-free condition because their magnetic energy is dominated by magnetic pressure.Plasma pressure in the magnetosphere is far less than magnetic pressure so it can be ignored.In this paper,we tried to find the variable separated stream function solution around the surface of magnetar under force-free condition and carry out numerical simulation of field lines,as well as numerical calculation of twist angle and magnetic energy.