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On Deflection of Solar Coronal Mass Ejections by the Ambient Coronal Magnetic Field Configuration

Solar Coronal Mass Ejections (CMEs) are sometimes deflected during their propagation. This deflection may be the consequence of interaction between a CME and a coronal hole or the solar wind. We analyze 44 halo-CMEs whose deflection angle exceeds 90 degrees. The coronal magnetic field configuration is computed from daily synoptic maps of magnetic field from SOHO/MDI and SDO/HMI using a Potential Field Source Surface (PFSS) model. By comparing the ambient magnetic field configuration and the measured position angles (MPA) of the CMEs, we conclude that the deflection of 80% of the CMEs (35 of 44) are consistent with the ambient magnetic field configuration, agreeing with previous studies. Of these 35, 71% are deflected toward the heliospheric current sheet (HCS), and 29 degrees toward a pseudo-streamer (PS), the boundary between the same-polarity magnetic field regions. This implies that the ambient coronal magnetic field configuration plays an important and major role in the deflection of CMEs, and that the HCS configuration is more important than PS. If we exclude 13 CMEs having much higher uncertainty from the sample, the agreement between the deflection of CMEs and the ambient field configuration increases substantially, reaching 94% in the new sample of 31 CMEs.