J. Geophys. Res. 111 (A4), A04105, 2006
© American Geophysical Union
Tracking halo coronal mass ejections from 0−1 AU and space weather forecasting
using the Solar Mass Ejection Imager (SMEI)
T.A. Howard
School of Physics and Astronomy, University of Birmingham, Edgbaston, UK
D.F. Webb
Inst. for Scientific Research, Boston College, MA, USA
S.J. Tappin
School of Physics and Astronomy, University of Birmingham, Edgbaston, UK
D.R. Mizuno
Inst. for Scientific Research, Boston College, MA, USA
J.C. Johnston
Space Weather Center of Excellence, Air Force Research Laboratory, Hanscom AFB, MA, USA
Abstract
The Solar Mass Ejection Imager (SMEI) has been tracking coronal mass ejections (CMEs) from the Sun to
the Earth and beyond since it came online in February 2003. This paper presents some results from the
first 19 months of data from SMEI, when over 140 transients of many kinds were observed in SMEI's
all-sky cameras. We focus specifically on 20 earthward directed transients, and compare distance-time
plots obtained from the SMEI transients with those observed in halo CMEs by Large-Angle Spectrometric
Coronograph (LASCO) aboard Solar and Heliospheric Observatory (SOHO), and the arrival time of the
shock observed by ACE at 0.99 AU. The geometry of one particular transient is compared using both
LASCO and SMEI images in a first attempt to investigate geometry evolution as the transient propagates
through the interplanetary medium. For some events, the halo CME, SMEI transient, and shock at 0.99 AU
do not match, suggesting that some transients may not correspond to a halo CME. Finally, an evaluation
of the potential of SMEI to be used as a predictor of space weather is presented, by comparing the
transients observed in SMEI with the 22 geomagnetic storms which occurred during this timeframe.
A transient was observed in 14 cases, and distance-time profiles would have allowed a prediction of
the arrival time at ACE within 2 hours of its actual arrival for three events, and within 10 hours
for eight events. Of these eight events, seven were detected by SMEI more than 1 day before the
transient's arrival at the Earth.