Two similar major coronal mass ejections (CMEs) occurring on October 28 and November 18, 2003 were reported. Through the comparison of the two CMEs as well as their interplanetary responses, two primary space weather effects of them, i.e., solar energetic particle (SEP) events and large geomagnetic storms, were studied. The associated solar activities of both CMEs involved at least one large flare, a preceding minor fast CME and an eruption of filament. An extremely intense gradual SEP event was produced by the former CME, but no major SEP event appeared after the latter. However, they both caused a great geomagnetic storm and the storm created by the latter CME was slightly larger than the former. By analyzing observations of the two CMEs, their associated activities and the corresponding interplanetary magnetic clouds (MCs), the reasons why the two similar major CMEs caused different consequences in the geo-space were discussed. The difference between the two CMEs with respect to SEP events is due to the evident different release rate of energy, and the similarity and difference in geomagnetic storms are related to the MC orientations and the paths along which the Earth intersects the MCs.%研究了分别发生在2003年10月28日和2003年11月18日的两次相似的强烈日冕物质抛射(CME)事件.通过比较这两次CME事件以及它们的行星际响应,分析了其伴随的两种主要空间天气效应:太阳高能粒子事件和地磁暴.这两次CME事件均伴随有一个强耀斑和一次暗条爆发,并且之前都有一个较弱的CME从同一源区产生.第一个CME事件引起了一次极大的太阳高能粒子事件,而第二个则没有引起明显的太阳高能粒子事件.这两次CME事件均引起了大的地磁暴,且第二个CME所引起的地磁暴比第一个CME所引起的地磁暴更强.通过比较分析这两次CME事件, 以及与之相关的活动现象和对应的行星际磁云(MC),讨论了这两次CME引起不同空间天气效应的原因:形成不同强度的太阳高能粒子事件在于CME爆发过程中的能量释放率在这两次事件中显著不同,而地磁暴强度的差异则是由行星际MC轴的方向以及MC经过地球时的相对位置不同造成的.
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