利用跨极区极光弧形态北向IMF条件下变形的地球磁层中的等离子体诊断

太阳风-磁层-电离层耦合过程中的一个关键问题 "夜侧扭曲跨极区极光弧（TPA）"与大尺度等离子体输运以及夜侧磁重联过程有密切的关系。通过对相关问题的研究，将有助于阐明夜侧扭曲TPA现象的形成机制，以揭示等离子体、能量和磁通量从受行星际磁场（IMF）影响而形变的磁层向电离层传输的过程。.因此本项目将利用TPA这一自然现象作为诊断工具，通过卫星以及地面观测台站的遥感数据观测研究IMF条件对全球磁层形变的过程以及其带来的影响。预计本项目完成时将能阐明1）等离子体、能量和磁通量是如何通过夜侧磁重联形成夜侧扭曲TPA的；2）相关的电离层等离子体流动模式与磁尾的等离子体传输之间的关系。该项目的研究结果不仅有助于理解独特形态TPA（夜侧扭曲）的形成过程，还可以了解形变磁层内的等离子体、能量和磁通量输运情况。

The terrestrial magnetosphere is perpetually exposed by the high-speed plasma streams (solar wind) and Interplanetary Magnetic Field (IMF) originating from the Sun, which significantly affect the internal magnetospheric processes. Magnetic reconnection plays an essential role in transferring the plasma and energy from the external solar wind to magnetosphere or from the magnetotail to ionosphere. Even under northward IMF conditions, plasma is transferred through magnetic reconnection occurring in the nightside plasma sheet and magnetotail lobe. Furthermore, if taking into account significant effect of the dawn-dusk IMF component (IMF-By) to the magnetosphere, such as the nightside magnetospheric deformation, the plasma and energy transfer profiles under the northward IMF are considered to be more complicated than those during simple north and southward IMF intervals..Transpolar Arc (TPA) is one of the most representative auroral phenomena occurring under northward IMF conditions, and their formations are closely related with the magnetospheric deformations due to the IMF-By component. Therefore, TPA can be a useful tool to globally diagnose the plasma transfer from the deformed magnetotail to the ionosphere. Recently, the global auroral imager camera onboard IMAGE detects the TPAs with distortions at their nightside ends. The dawnside (duskside) TPAs had the nightside ends distorted toward pre- (post-) midnight. These TPAs are identified as “nightside distorted TPAs”, or “J”- and “L”-shaped TPAs based on their resemblance to the letters “J” and “L”. Their source is considered Field-Aligned Currents (FACs) driven by plasma flow shear between the earthward fast flows generated by nightside reconnection and slower background magnetospheric flows. The TPA growth to the dayside is attributed to the tailward retreat of the reconnection points. Therefore, a global plasma transfer profile from the IMF-deformed magnetotail to the ionosphere is obtained via the elucidation of the nightside distorted TPA formation process..In this project, we try to investigate 1) how plasma, energy, and magnetic flux are transported earthward through magnetotail reconnection during the nightside distorted TPA intervals, 2) how associated ionospheric plasma flow patterns, and FAC structures can be observed, and 3) what the significant differences in plasma and energy transport profiles between conventional and nightside distorted TPAs are. To resolve these questions, we examine the data obtained from concomitant space- and ground-based observations of aurora image, in-situ magnetotail, HF (high frequency) radar and geomagnetic field. The results obtained through this study can be an important clue to resolve the plasma transfer within a framework of Solar Wind-Magnetosphere-Ionosphere coupling.