Propagation Characteristics of CMEs Associated with Magnetic Clouds and Ejecta
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We have investigated the characteristics of magnetic cloud (MC) and ejecta (EJ) associated coronal mass ejections (CMEs) based on the assumption that all CMEs have a flux rope structure. For this, we used 54 CMEs and their interplanetary counterparts (interplanetary CMEs: ICMEs) that constitute the list of events used by the NASA/LWS Coordinated Data Analysis Workshop (CDAW) on CME flux ropes. We considered the location, angular width, and speed as well as the direction parameter, D. The direction parameter quantifies the degree of asymmetry of the CME shape in coronagraph images, and shows how closely the CME propagation is directed to Earth. For the 54 CDAW events, we found the following properties of the CMEs: i) the average value of D for the 23 MCs (0.62) is larger than that for the 31 EJs (0.49), which indicates that the MC-associated CMEs propagate more directly toward the Earth than the EJ-associated CMEs; ii) comparison between the direction parameter and the source location shows that the majority of the MC-associated CMEs are ejected along the radial direction, while many of the EJ-associated CMEs are ejected non-radially; iii) the mean speed of MC-associated CMEs (946 km s−1) is faster than that of EJ-associated CMEs (771 km s−1). For seven very fast CMEs (≥ 1500 km s−1), all CMEs with large D (≥ 0.4) are associated with MCs and the CMEs with small D are associated with EJs. From the statistical analysis of CME parameters, we found the superiority of the direction parameter. Based on these results, we suggest that the CME trajectory essentially determines the observed ICME structure.
KeywordsCoronal mass ejections, ejecta Interplanetary coronal mass ejections, magnetic clouds
This work benefited from the NASA/LWS Coordinated Data Analysis Workshops on CME flux ropes in 2010 and 2011. We acknowledge the workshop support provided by NASA/LWS, Predictive Sciences, Inc. (San Diego, CA), University of Alcala (Alcala de Henares, Spain), and Ministerio de Ciencia e Innovacion (Reference number AYA2010-12439-E), Spain. This work was partially supported by the Construction of Korean Space Weather Center as the project of KASI, the KASI Basic Research Fund, and Research Fellowship for Young Scientists of KRCF. Y.-J.M. has been supported by the WCU program (No. R31-10016) and Basic Research Promotion Fund (20090071744 and 20100014501) through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology.