黑子磁场的Stokes光谱反演技术

对太阳大气磁场的可靠测量有助于人们更好地理解太阳活动区内外的许多活动现象,如耀斑的触发和能量释放过程、黑子的形态和黑子大气的平衡、日珥的形成等.由于原子在磁场中的一些能级会产生分裂(Zeeman效应),使对应这些能级的谱线分裂成若干个具有不同偏振特性的分量,因此目前对黑子磁场的测量主要是通过偏振光,即Stokes参量I、Q、U、V的观测来实现的.该文主要介绍近30年来太阳黑子光谱反演的方法以及所取得的成就;同时也对光谱反演和滤光器型的望远镜矢量磁场的测量进行了简单的比较.

Stokes Inversion Techniques of Sunspots' Magnetic Fileld

Reliable measurements of vector magnetic field in the solar atmosphere will help us with a better understanding of many active phenomena in association with solar active regions, such as the trigger mechanism and energy release of flares,the structure and dynamics of sunspots, the formation of prominences and so on.At present,the high resolution observations have mostly been made on various small-scale magnetic structures with regard to the rather large-scale and strong fields in sunspots. Because some energy levels of an atom will split in the magnetic field(Zeeman effect),spectral lines corresponding to these energy levels will exhibit different components with various characters of polarization.At present,the measurements of sunspots' magnetic field are carried out by the observations of Stokes parameters I,Q,U and V in a spectral line sensitive to the Zeeman effect.In this paper we will summarize the progress of Stokes inversion techniques of sunspots' magnetic fields,which have been made in recent 30 years. Furthermore,we will present a brief comparison between the two kinds of optical instruments for the solar vector magnetic field's research,namely the spectrograph represented by the grating spectrograph and the filter represented by the birefringent filter.The review is aimed at future studies on sunspot Stokes polarimetry based on the high resolution observations from spaceborne, e.g.,Solar-B polarimeter,and ground-based observations.