Solar source of non-spiral interplanetary magnetic field

非帕克型行星际磁场来源于太阳上的非静态源，有望成为研究太阳风及其太阳源的关键。正如在Yohkoh软x射线图像中所认识到的那样，光球上有各种各样的活动，这些活动将喷射物释放到行星际空间中。由于在行星际航天器上的点观测很容易遗漏，因此很难识别出所有与喷射物对应的行星际物。研究行星际空间的非螺旋磁场，进而研究它们与太阳现象的关系，是比较方便的。本研究利用GEOTAIL航天器获得的磁场和低能粒子数据，对具有平面磁性结构的非帕克型行星际物体进行了研究。在平面磁性结构中，磁场矢量都平行于一个倾斜于黄道面的平面。先前的研究表明，这些来源往往与活跃区域的扩张相吻合。利用GEOTAIL上的低能粒子（LEP）实验，研究了低能电子在平面磁性结构中的角分布，以检验其与光球的磁连接。在平面磁性结构中没有发现闭合场线的双向电子特征。以往的研究表明，磁场的跳跃是切向不连续的，但由于缺乏对太阳风速度的高时间分辨率观测，尚未对速度跳跃进行研究。本研究采用GEOTAIL/LEP数据计算结构面法向速度分量Vn和不连续面传播速度U。结果表明，跳跃是切向不连续的，其中速度U等于Vn。

Non-Parker type interplanetary magnetic field comes from non-static source on the Sun, and is expected as a key that relates solar wind and its solar source. As has been recognized in the Yohkoh soft X-ray images, there are various activities on the photosphere which release ejecta into interplanetary space. It is difficult to identify all the interplanetary counterparts of the ejecta because they can be easily missed by point observation from interplanetary spacecraft. It is more convenient to examine non-spiral magnetic field in interplanetary space and then to investigate their relationship to the solar phenomena.In this study, non-Parker type interplanetary objects, planar magnetic structures, have been examined by using magnetic field and low-energy particle data obtained by GEOTAIL spacecraft. In a planar magnetic structure, magnetic field vectors are all parallel to a plane that is inclined to the ecliptic plane. Previous study showed that the sources often coincided with expanding ioops from active regions. In order to examine their magnetic connection to the photosphere, angular distribution of low-energy electrons in planar magnetic structures were examined by using Low Energy Particle(LEP) experiment onboard GEOTAIL.Bidirectional electrons characteristic of closed field lines were not found in planar magnetic structures.Previous studies suggested that the jumps in magnetic field were tangential discontinuities, however, velocity jumps had not been investigated because of lack of high-time resolution observation of the solar wind velocity. In this study, GEOTAIL/LEP data were used to calculate velocity component Vn normal to the plane of the structure and the propagation speed U of the discontinuity surface. It resulted in that the jumps were tangential discontinuities in which the speed U was equal to Vn.