Combined loop stereoscopy and field extrapolations in active regions

The 3d magnetic corona   The solar magnetic field couples the solar interior with the photosphere and corona where it drives heating processes and eruptive phenomena. In the corona the magnetic energy is quasi-statically built up until it exceeds by far the energy stored in a potential magnetic configuration. This excess energy is intermittently released in parts by large eruptive phenomena, e.g. coronal mass ejections, flares and eruptive prominences, but also through small ones, such as explosive events and nano- and micro flares which are probably central for heating the solar corona. Knowledge regarding the coronal magnetic field therefore plays a key role for obtaining a better understanding of these phenomena. Most measurements of the magnetic field vector are restricted to the photosphere, so that the magnetic field needs to be extrapolated from there into the corona. High resolution vector magnetograms are available from ground based (SOLIS), balloon-born (Sunrise) and space born instruments (Hinode, SDO, in future Solar Orbiter). Codes for modelling the coronal magnetic field have been developed at the MPS and are continuously improved.