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Active region 11856 was observed on the solar surface in October 2013. It provides an example of emerging flux within an already established active region – the distribution of the magnetic field at the photoshperic boundary shows that a bipolar structure emerges into the existing field over a period of a few hours. The timing of the flux emergence coincides with a C-class solar flare and also seems to trigger the disappearance of the leading sunspot present in the initial configuration.
The active region is studied using a potential field model to extrapolate the magnetic field from the SDO/HMI HARP series magnetograms. This then reveals the topological changes in the magnetic field due to the changes in flux as it evolves, with a focus on the domains of connectivity and reconnection of the field lines and the locations of null points in the field. The model also provides the change over time of the magnetic energy of the active region.