Multipoint Study of Magnetic Cloud Structures and the Associated Solar Origins

• Main Authors: Pei-Hsuan Lin, 林沛萱
• Other Authors: Ya-Hui Yang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/00104289731005883292

碩士 === 國立中央大學 === 太空科學研究所 === 104 === Magnetic cloud (MC) is one subset of the interplanetary coronal mass ejection (ICME), which is an important large-scale structure in the interplanetary space. In this study, we use the in-situ solar wind data provided by STEREO and Wind spacecrafts to analyze the properties and global configurations of six MC events. We attempt to clarify the difference between the classical large-scale flux rope model and observations. Each analyzed event has complete data coverage measured by at least two spacecrafts. The flux rope parameters of MCs are derived from a linear force-free field fitting. In addition, we identify the associated solar origins based on coronagraph images from STEREO/COR1&2 and SOHO/LASCO C2, multi-wavelength images from STEREO/EUVI and SOHO/EIT, photospheric line-of-sight magnetograms from SOHO/MDI, and ground based Hα images from BBSO. Our results show that the flux rope radius could be quite different but the central axial magnetic field strength would be similar at different locations of a MC. Magnetic helicity sign of a MC is found to remain invariant from the solar source region to the interplanetary space. It is also found that the scale of a MC in the axial direction can extend to 0.8 AU. All the above properties can be explained by the classical large-scale MC flux rope model. Note that the distorted flux rope magnetic fields due to the interaction with other solar wind structures would affect the fitting results. Half of the studied MC events do not have the strong solar explosions, which implies that the MCs at 1 AU may have weak correspondence with the magnitude of solar activity in source regions.