CORONAL MASS EJECTIONS AND GLOBAL CORONAL MAGNETIC FIELD RECONFIGURATION

We investigate the role of coronal mass ejections (CMEs) in the global coronal magnetic field reconfiguration, a debate that has lasted for about two decades. Key evidence of the coronal field restructuring during the 2007 December 31 CME is provided by combining imaging observations from widely separated spacecraft with the potential-field source-surface (PFSS) model, thanks to the extraordinarily quiet Sun at the present solar minimum. The helmet streamer, previously disrupted by the CME, re-forms but is displaced southward permanently; the preexisting heliospheric plasma sheet (HPS) is also disrupted as evidenced by the concave-outward shape of the CME. The south polar coronal hole shrinks considerably. Plasma blobs moving outward along the newly formed HPS suggest the occurrence of magnetic reconnection between the fields blown open by the CME and the ambient adjacent open fields. A streamer-like structure is also observed in the wake of the CME and interpreted as a plasma sheet where the thin post-CME current sheet is embedded. These results are important for understanding the coronal field evolution over a solar cycle as well as the complete picture of CME initiation and propagation.