[1] Kiepenheuer Inst Sonnenphys, Schoneckstr 6, D-79104 Freiburg, Germany
[2] Univ Oslo, Inst Theoret Astrophys, POB 1029 Blindern, N-0315 Oslo, Norway
[3] Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany
[4] Kyung Hee Univ, Sch Space Res, Yongin 446701, Gyeonggi Do, South Korea