[Previous] | [Session 2] | [Next]
D.F. Webb (ISR, Boston College), R.P. Lepping (LEP, NASA GSFC), N.U. Crooker (CSP, Boston University), S.P. Plunkett (USRA/NRL, NASA GSFC), O.C. St. Cyr (CPI/NRL, NASA GSFC)
The SOHO LASCO coronagraphs have observed many halo-like CMEs since 1996. Halo CMEs launched toward Earth are important because: 1) their source regions can be well observed on the solar disk, 2) in-situ plasma and IMF measurements by near-Earth spacecraft can probe the internal structure along their central axes, and 3) their effects on geomagnetic activity can be better understood. For example, recent studies have shown that most halo CMEs associated with frontside, near-Sun center surface activity were followed 2-5 days later by shocks, magnetic clouds and moderate storms at Earth. Here we report on the results of two aspects of a study of all full halo CMEs observed through 1999. First, we compare the evolution of the CMEs near the Sun with in-situ measurements when the ejecta arrive at the Wind and ACE spacecraft to better understand the internal structure of CMEs. Second, we compare the location and timing of the southward fields within the ICMEs with the storm development at Earth as a measure of their geoeffectiveness.