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S. Gibson, B.C. Low, Y. Fan (NCAR/HAO), L. Fletcher (University of Glasgow)
The interaction between emerging magnetic structures and preexisting overlying coronal structures will be addressed using a combination of observations and physical models that incorporate a range of twisted magnetic topologies. Solar explosive events such as coronal mass ejections (CMEs) and flares are commonly considered to be driven by the free magnetic energy stored in twisted (current carrying) coronal magnetic fields. Understanding the origin and the three-dimensional nature of these twisted coronal magnetic structures is a crucial step towards explaining and predicting CMEs and flares. One possible and appealing picture is that the twisted coronal magnetic structures form as a result of the emergence of twisted magnetic flux tubes from the solar interior. We might imagine a scenario where a flux rope forms sub-photospherically, emerges through the photosphere, exists in the corona until it loses its stability and erupts in a CME which moves out through interplanetary space until ultimately impacting on the Earth's magnetosphere. Attractively simple as this picture is, reality is likely to be more complicated since the various regimes are physically very different and pre-existing structures would get in the way of our traveling flux rope. We will concentrate on joining up two of these regimes, by considering how a flux rope could rise from beneath the photosphere and emerge into the corona, interacting with pre-existing coronal structures. We will approach this problem by using a combination of numerical models of the flux rope emergence from beneath the photosphere, analytic models of coronal dynamic and equilibrium magnetic structures, and photospheric and coronal observations of the 3-d structure and evolution of a so-called "sigmoidal", or S-shaped active region. In so doing we hope to gain essential insight into how twisted magnetic fields are formed and how they could be ultimately removed from the solar corona.
The author(s) of this abstract have provided an email address for comments about the abstract: sgibson@hao.ucar.edu
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.