Remote Sensing Observations of the late October 2003 Geoeffective Halo CMEs

Eleven major (X-class) flares with accompanying coronal mass ejections (CMEs) occurred over the 2-week period in late October and early November. These were part of a series of major events centered around 3 huge sunspot groups. The largest geoeffective event occurred on October 28, had the third highest peak X-ray flux (X17) ever recorded, and was followed by another energetic event (X10) on October 29. At least 3 of the CMEs from this activity were Earth-directed ("halos"), which erupted when the sunspot regions were near Sun center, and caused geomagnetic storms. The 2 strongest storms, driven by the fast CMEs from the X17 and X10 events, occurred on October 28-30 yielding peak Dst values of -363 and -401, resp. The earliest halo CME was associated with M-class flares and at least two erupting filaments on October 22. It produced only minor storminess at Earth because its magnetic field was mostly northward. The Air Force Solar Mass Ejection Imager (SMEI) on the Coriolis satellite captured images of two of the 3 halo CMEs, on October 23 and 29. We compare the SMEI observations with SOHO LASCO coronagraph and EIT observations and Interplanetary Scintillation (IPS) observations of the events to study their structure and kinematics. SMEI observed these halo CMEs starting at angular distances of 28 and 21 deg. from the Sun, or about 1/3 of the way from the Sun to Earth. These observations demonstrate that SMEI can detect even fast, Earth-directed CMEs up to a day before their arrival.