Impact of Major Coronal Mass Ejections on Geospace during 2005 September 7–13

Abstract

We have analyzed five major CMEs originating from NOAA active region (AR) 808 during the period of 2005 September 7–13, when the AR 808 rotated from the east limb to near solar meridian. Several factors that affect the probability of the CMEs’ encounter with the Earth are demonstrated. The solar and interplanetary observations suggest that the second and third CMEs, originating from E67 � and E47 � , respectively, encountered the Earth, while the first CME originating from E77 � missed the Earth, and the last two CMEs, although originating from E39 � and E10 � , respectively, probably only grazed the Earth. On the basis of our ice cream cone mode and CME deflection model, we find that the CME span angle and deflection are important for the probability of encountering Earth. The large span angles allowed the middle two CMEs to hit the Earth, even though their source locations were not close to thesolar centralmeridian.ThesignificantdeflectionmadethefirstCMEtotallymisstheEartheventhoughitalsohad wide span angle. The deflection may also have made the last CME nearly miss the Earth even though it originated close to the disk center. We suggest that, in order to effectively predict whether a CME will encounter the Earth, the factors of the CME source location, the span angle, and the interplanetary deflection should all be taken into account.