Tracking a major interplanetary disturbance with SMEI

Abstract

We present the first clear observations of an Earth-directed interplanetary disturbance tracked by the Solar Mass Ejection Imager (SMEI). We find that this event can be related to two halo CMEs seen at the Sun about 2 days earlier, and which merged in transit to 1 AU. The disturbance was seen about 16 hours before it reached Earth, and caused a severe geomagnetic storm at the time which would have been predicted had SMEI been operating as a real-time monitor. It is concluded that SMEI is capable of giving many hours advance warning of the possible arrival of interplanetary disturbances. Copyright 2004 by the American Geophysical Union.