Evolution of coronal magnetic fields

• Applicant: Dr. Thomas Wiegelmann
• Subject Area: Astrophysics and Astronomy
• Term: from 2006 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 26559079

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. 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. Within this project we propose to use a non-linear force-free optimization code to compute the 3D coronal magnetic field from photospheric measurements. A force-free description of the coronal magnetic field is justified due to the low ß plasma in the low and middle corona. The study aims to investigate the temporal quasi-static evolution of active regions with the aim of getting insights into the conditions required for flares and CMEs, as well as for explosive events and micro flares.

• DFG Programme: Research Grants