Flows and Magnetic Fields in Complex Sunspots and their Role in Producing Solar Flares

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Coronal mass ejections (CMEs) and flares are the most prominent energetic events on the Sun, which can even affect the Earth and the near-Earth environment. In today’s technology-driven society, precise knowledge about the likelihood of such eruptive events and effective ways of forecasting their occurrence are essential to protect assets both in space and on the ground. However, many fundamental questions remain open about the nature of flares and the mechanisms that trigger them. Recently, rapid changes of photospheric magnetic fields have been observed after solar flares, where entire segments of sunspot penumbrae permanently vanished. Shear flows along the magnetic neutral line are an example of peculiar flows in complex sunspots, which might contribute to magnetic shear buildup and lead to non-potential magnetic fields. Two-dimensional spectroscopy and polarimetry with high spatial, temporal, and spectral resolution provides an excellent opportunity to study these phenomena and to advance our understanding of the complex and highly dynamic nature of sunspots. This research project is one of the key science projects for the GREGOR solar telescope, which will become operational at Observatorio del Teide, Tenerife, Spain in the summer of 2011. The GREGOR Fabry-Pérot Interferometer (GFPI) will be used during the GREGOR science demonstration in 2011–14 to zoom in on the small-scale processes associated with solar flares, while additional data from ground-based and (new) space missions will provide the necessary context.