Observational Evidence for Rising Penumbral Flux Tubes?

• Published in: Solar physics Vol. 241; no. 2; pp. 223 - 233
• Main Authors: Jurcak, J, Sobotka, M
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01-04-2007
• Subjects: Magnetic fields; Solar physics; ASE, Atlantic, Canary Is., La Palma
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/s11207-007-0367-7

On 13 May 2000 parts of a penumbra were observed in an active region NOAA 8990 with the La Palma Stokes Polarimeter attached to the Swedish Vacuum Solar Telescope. The stratification over the solar atmosphere of different physical parameters is retrieved from these data by using the Stokes inversion based on response functions. The results confirm the previous findings of the penumbral structure. In general, the magnetic field becomes weaker and more horizontal with increasing distance from the umbra and the line-of-sight velocities are increasing towards the outer boundary of the penumbra. The results also suggest the existence of the unresolved fine structure of the penumbra. The stratifications of the temperature and of the magnetic field strength indicate the presence of rising flux tubes, which were predicted theoretically by Schlichenmaier, Jahn and Schmidt (1998, Astron. Astrophys.337, 897).