| 脉冲星磁场的演化 |
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| 引用本文： | 孙晓辉,韩金林.脉冲星磁场的演化[J].天文学进展,2002,20(2):130-143. |
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| 作者姓名： | 孙晓辉 韩金林 |
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| 作者单位： | 北京大学天文系,北京,100871;中国科学院国家天文台,北京,100012;中国科学院-北京大学联合北京天体物理中心,北京,100871 |
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| 基金项目： | 国家自然科学基金(19903003,10025313)资助课题 |
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| 摘 要： | 综述了前人对于单个脉冲星磁场的起源和演化的研究结果及其最新进展。脉冲星磁场的起源有多种模型，其所对应的初始磁场有两种位形：磁场束缚在核内和磁场束缚在壳层中。脉冲星的磁场如何演化，没有一致的结论。有各种观测证据可能直接或间接表明磁场的演化行为，如根据特征年龄和运动学年龄的差异可以推断出脉冲星磁场按指数规律衰减，而根据特征年龄与超新星遗迹年龄的差异或几颗年轻脉冲星的制动指数可以认为年轻脉冲星的磁场可能是增强的。脉冲星的样本合成研究（数值模拟）是研究脉冲星磁场演化的重要方法。模拟结果表明，假定脉冲星磁场按指数衰减，特征衰减时标必须为10^7yr或更长。而壳层中磁场的欧姆耗散模型数值计算显示脉冲星磁场演化行为因冷却模型和状态方程的取法不同而异，但最终无明显的衰减。由自转变慢诱导的脉冲星核内部磁场向壳层中扩散模型的计算表明脉冲星磁场的衰减只发生在10^7-10^8yr这段时间内，磁场衰减1－2个量级。
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| 关 键 词： | 脉冲星 磁场 衰减 数值模拟 欧姆耗散模型 |
| 修稿时间： | 2001年7月17日 |
Evolution of Normal Pulsar Magnetic Fields |
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| Sun Xiaohui Han Jinlin.Evolution of Normal Pulsar Magnetic Fields[J].Progress In Astronomy,2002,20(2):130-143. |
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| Authors: | Sun Xiaohui Han Jinlin |
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| Abstract: | Results and new progress of the origin and evolution of pulsar magnetic fields are reviewed.Lots of models about how such strong magnetic fields were generated, mainly two kinds of struc-tures were proposed for initia1 magnetic fields: fields confined in the cores and fields confined inthe crusts of neutron stars. No consensus has been reached on whether the magnetic fields decayor not, despite some observational evidence for the evolution of magnetic fields. The discrepancybetween characteristic ages and kinematics ages indicates that the magnetic fields decay expo-nentially. On the other hand, the braking indices of several young pu1sars and the comparisonbetween pulsar characteristic ages and the ages of associated supernova remnants suggest thatthe magnetic fields of young pulsars grow like a power-law. Pulsar population synthesis is one ofthe most important methods to investigate the evolution of magnetic fields. Many simulationsshow that if magnetic fields do decay exponentially, the e-folding decay time should be 100 Myror longer. The numerical calculations of the Ohmic decay in the crust indicate that the scenarioof exponential decay is oversimp1e, and the evolution could be divided into four possible phasesapproximately: exponential decay, no decay, power-law decay and exponential decay again. Themodel of magnetic fields expulsion induced by spin-down suggests that the magnetic fields decayonly in a period between 107 yr and 108 yr. |
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| Keywords: | pu1sar-magnetic field-methods: statistical-decay |
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