Earthward directed CMEs seen in large-scale coronal magnetic field changes, SOHO LASCO coronagraph and solar wind

One picture of coronal mass ejection (CME) initiation relates these events to the expansion into space of previously closed coronal magnetic fields, o ften part of the helmet streamer belt. The work described here makes use of the potential field source surface model based on updated synoptic photosp heric field maps to study the large-scale coronal field changes. We isolate those field lines that change from closed to open configurations (newly op ening field lines) by comparing potential field source surface models from adjacent magnetograph observations, wherein the same starting foot points o n the photosphere are used. If there are some newly opening field lines bet ween the times of two maps, we assume there was a possibility for CME occur rence(s) between these times. In particular, if there are newly opening fie ld lines near the solar disk center, an earthward directed CME may have bee n generated. Monitoring the coronal magnetic field behavior can in principl e reinforce (or not) days in advance predictions of magnetic storms based o n Solar and Heliospheric Observatory (SOHO) Large-Angle Spectrometric Coron agraph (LASCO) halo CMEs. Moreover, the coronal field over the visible hemi sphere contains information about the possible geoeffectiveness of a partic ular CME because it shows the approximate orientation and location of the a ctive arcades. By comparing halo CMEs with the newly opening field lines, t he solar wind measurements from Wind and ACE spacecraft and the Dst index, we show that, like soft X-ray sigmoids, disappearing filaments, and Extreme ultraviolet Imaging Telescope (EIT) waves on the disk of the Sun, magnetog raph observation-based coronal field models may provide additional informat ion on the likelihood of CME effects at the Earth.