How Pre-Eruption Configurations Lead to Bz in the Corona

Abstract:

One of the key properties that determines the strength of geomagnetic disturbances is the pattern of the magnetic field contained in coronal mass ejections (CME), often summarized in the term 'Bz' that characterizes the field orientation in the leading segment of the CME. That Bz has its origin in the field that leaves the solar corona at the initial phases of the eruption, and is thus set by the properties of the erupting active region field and the field into which the eruption initially propagates. Mapping the 3D configuration of these fields remains a challenge, but as observational and modeling capabilities advance, we can expect to improve our knowledge of the field leaving the Sun. I will review the current status of our capabilities to model the 3D field above solar active regions, summarize our growing skills at using observations of solar surface and corona to drive these models, and discuss opportunities for the near future.