| 其他摘要 | Coronal Mass Ejections (CMEs) are the most violent explosive phenomena in the solar atmosphere and the main driving source of disastrous space weather. In this thesis, I use the observational data of ACE spacecraft to conduct a detailed study on the internal characteristics of the magnetic flux rope structure (i.e., magnetic cloud, abbreviated as MC) propagating in interplanetary space of CME. The results show that MCs have specific interior structures, and MCs of different speeds show differences in composition and structure. Compared with the slow MCs, fast MCs have enhanced mean charge states of iron, oxygen, silicon, magnesium, O7+/O6+,C6+/C4+,C6+/C5+,Fe16+/Fetotal. For ionic species in fast MCs, a higher atomic number represents a greater enhancement of mean charge state than slow MCs. We also find that both the fast and slow MCs display bimodal structure distributions in the mean iron charge state, which suggests that the existence of flux rope prior to the eruption maybe common. Furthermore，the mean iron charge state，O7+/O6+ and Fe16+/Fetotal ratio distribution inside fast MCs have the feature that the posterior peak is higher than the anterior one. This result agrees with the “standard model” for coronal mass ejection/flares, by which magnetic reconnection occurs beneath the flux rope, thereby ionizing the ions of the posterior part of the flux rope sufficiently by high-energy electron collisions or by direct heating in the reconnection region.The origin of small-scale interplanetary magnetic flux-ropes (SIMFRs) and the relationship between SIMFRs and MCs are still controversial. In this study, two populations of SMIFRs were collected, i.e., SIMFRs originating from the Sun (SIMFR-SUN) and those originating from the solar wind (SIMFR-SW). We defined the SIMFR-SUN (SIMFR-SW) as the SMIFRs that include (exclude) the counter-streaming suprathermal electrons and stay away from (close to) the heliospheric current sheet. After fitting with force-free flux-rope model, 52 SIMFR-SUN and 57 SIMFR-SW events observed by ACE from 1998 February to 2011 August were qualified. Using the approach of relating the measurements to their spatial position within the flux-ropes, a statistical survey of plasma and composition characteristics inside the two populations of SIMFRs is presented. Results show that the two populations of SIMFRs have apparent differences. Compared with SIMFR-SW, SIMFR-SUN are MC-like, featuring lower central proton density, higher radial velocity, higher low-FIP element abundances, higher and more fluctuate average ion charge-states and the ion charge-state ratios which are related to the heating in low corona. In addition, for the ion charge-state distributions inside SIMFR-SUN, the sunward side is higher than earthward, which might be caused by the flare heating during eruption. Moreover, both SIMFR-SUN and MCs show anti-correlation between plasma beta and He/P trend. These characteristics indicate that SIMFR-SUN and MCs are very likely to have the identical origination. This study supports the two-source origin of SIMFRs, i.e., the solar corona and the solar wind. Generally, due to the difference of source region, the interplanetary magnetic flux-ropes have different internal properties and characteristics in the solar wind. These characteristics also help us to infer the environmental and physical processes of the source region. |
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