脉冲星辐射区结构研究

Study on the Structure of Emission Regions of Pulsars

为了研究脉冲星本质与磁层动力学过程,如何从观测限定脉冲星辐射区域的部位和几何结构是其中一个基本且关键的问题.介绍了目前各种脉冲星辐射区几何限定方法的主要思想和结果,并对其异同和各自的优势作了比较和评述;根据已有的限定结果总结了其对辐射束结构、加速区模型和射电辐射机制等理论问题研究的帮助和启示;从各种方法的发展过程来看,完善能够限定脉冲星多波段辐射区域三维结构的方法,并与辐射区和加速区等理论问题的研究更紧密地结合是该领域的重要发展方向.

Pulsars are neutron stars or strange stars that can generate rnultiwavelength radiation. What the structure of emission regions in pulsar magnetosphere might be is tightly related to some fundamental properties in pulsar research, e.g. the nature of pulsar （neutron star or strange star） and dynamical process in magnetosphere. Extensive studies have been focused on the radio emission height and some consensus have been reached, that is the radio emission heights of normal pulsars are usually less than a few percent of light cylinder radius, but the transverse structures, in both magnetic azimuth and colatitude dimensions, have not been well identified from observations for a large sample of pulsars. Although some constraints could be obtained from detailed observations, the structure of high energy emission regions still remains as a matter of debate in theoretical models of rnagnetospheric accelerators. Recently, there is progress in the methodology of constraining the structure, which is promising to push forward the research in this field. In this paper various methods to constrain the emission regions are reviewed. They are： the pure geometric methods, the relativistic methods, the interstellar scintillation methods and the rnultiwavelength synthetic method. The pure geometric methods, based on simple assumptions for beam geometry and dipolar magnetic field, are widely used, but are only capable of deriving the emission altitude. Relativistic methods are more advanced than pure geometric methods, because more effects that happen in pulsar magnetosphere, e.g. retardation, aberration and magnetic field line sweep-back effects, are involved. In the latest version of relativistic method, three-dimensional parameters of emission region could be constrained. The interstellar scintillation methods provide an independent way to constrain the transverse size of emission region. The above three kinds of methods have been used to constrain only the radio emission region. Recently, a synthetic method was proposed to constrain three-dimensional structure of rnultiwavelength （e.g. radio and gamma-ray） emission regions by using rnultiwavelength observational properties of pulsars. In this paper, the main ideas, the results, and comparison with the advantages of these methods are presented in details. Implications of the constrained results to theoretical problems, e.g. testing accelerator models and radio emission mechanisms are discussed. From the evolution trend of these methods, it is suggested that the future efforts should be tried to develop various methods that can be used to determine three-dimensional structures of rnultiwavelength emission regions and to apply it for a large sample of pulsars, combining with studies on related theoretical issues.