基金Supported by the National Natural Science Foundation of China under Grant Nos 40390150, 40674094 and 40523006, and the National Basic Research Programme of China under Grant No 2006CB806305.
基金The authors are grateful to Japanese WDC-C2 KY0T0 AE index service for presenting AU,AL and AE indices and to Goddard Space Flight Center,NASA for presenting data of the interpanaetary condition and auroradata.Thanks are also given to Cluster and Double-Star Data Center for providing data used in the study.This work was supported by the National Natural Science Foundation of China(Grant No.40390152)the State Key Basic Research Program(Grant No.G200000784)the XK100010404 of Beijing City,and the Space Weather Laboratory,Center for Space Science and Applied Research,CAS.