USING HALO CMES TO STUDY THE INTERNAL STRUCTURE OF CMES

David Webb

Abstract

The SOHO LASCO coronagraphs have observed many halo or partial-halo CMEs since early 1996. A halo CME, especially when associated with solar activity near sun center, is important because it suggests the launch of a geoeffective disturbance toward Earth. Because such events can be viewed along their central axes by near-Earth spacecraft, we can use them to better understand the internal structure of CMEs and magnetic clouds. A study of the geoeffectiveness of halo CMEs observed during the first half of 1997 showed that all halo CMEs associated with frontside, near-Sun center surface activity were followed 3-5 days later by shocks, magnetic clouds and moderate storms at Earth. We report on the results of extending this examination to all halo CMEs observed through 1999.

Authors: Webb, D.F., O.C. St. Cyr, B.J. Thompson, and R.A. Howard

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