1. Max Planck Institute for Astronomy, D-69117 Heidelberg, Germany
2. Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark
3. Ruprecht Karls University, Grabengasse 1, D-69117 Heidelberg, Germany
4. Rosseland Centre for Solar Physics, University of Oslo, PO Box 1029 Blindern, NO-0315 Oslo, Norway
5. Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, NO-0315 Oslo, Norway
6. Department of Theoretical Physics and Astronomy, Herzen University, St. Petersburg 191186, Russia
7. Department of Physics, Western Michigan University, Kalamazoo, MI 49008, USA
8. Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
9. Institute for Solar Physics, Department of Astronomy, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm, Sweden
10. Institute of Astronomy of the Russian Academy of Sciences, Pyatnitskaya st. 48, Moscow 119017, Russia
11. Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany