太阳磁场非势性研究中的光流技术法

The Optical Flow Technique on the Research of Solar Non-potentiality

综述了太阳磁场非势性研究中几种光流技术法,并进一步讨论了光流技术应用后可得到的新非势性参量。主要内容分为以下两部分:(1)光流技术法是近年来太阳磁场非势性研究中新兴起的一系列图像分析法的统称,主要包括LCT、ILCT、MEF、DAVE和NAVE。对它们的计算条件、适用范围和优缺点进行了详细说明和比较。(2)应用光流技术,人们可以由时间序列的磁图得到磁结构的光流,从而直接由观测资料计算求得磁力线足点的水平流速度,进而得出磁螺度流(磁螺度由光球向日冕的注入率)、太阳表面的感应电场,光球表面的非势磁应力(其面积分就是洛伦兹力)等一系列新的非势性参量。前期研究表明,这些参量与耀斑、日珥爆发、CME等大的太阳爆发事件密切相关。

Several optical flow techniques,which have being applied to the researches of solar magnetic non-potentiality recently,have been summarized here.And a few new non-potential parameters which can be derived from them have been discussed,too.The main components of the work are presented as follows：（1） The optical flow techniques refers to a series of new image analyzing techniques arisen recently on the researches of solar magnetic non-potentiality.They mainly include LCT（local correlation tracking）,ILCT（inductive equation combining with LCT）, MEF（minimum energy effect）,DAVE（differential affine velocity estimator） and NAVE（nonlinear affine velocity estimator）.Their calculating and applying conditions,merits and deficiencies, all have been discussed detailedly in this work.（2） Benefit from the optical flow techniques, the transverse velocity fields of the magnetic features on the solar surface may be determined by a time sequence of high-quality images currently produced by high-resolution observations either from the ground or in space.Consequently,several new non-potential parameters may be acquired,such as the magnetic helicity flux,the induced electric field in the photosphere,the non-potential magnetic stress（whose area integration is the Lorentz force）,etc.Then we can determine the energy flux across the photosphere,and subsequently evaluate the energy budget. Former works on them by small or special samples have shown that they are probably related closely to the erupting events,such as flares,filament eruptions and coronal mass ejections.