Die Erzeugung und Dissipation von solaren Magnetfeldern

• Applicant: Professor Dr. Wolfgang Schmidt
• Subject Area: Astrophysics and Astronomy
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 182502164

• Final Report Year: 2014

Final Report Abstract

Within this project, we successfully investigated different aspects of the generation and dissipation of magnetic fields in the Sun. We analysed two excellent spectro-polarimetric datasets of (1) the quiet Sun, observed with the balloon-borne solar telescope S UNRISE in June 2009 and, (2) the evolution of a sunspot during its early stages of formation observed with the German Vaccuum Tower Telescope in July 2009. In addition, we took advantage of archived sunspot observations obtained with the Tenerife Infrared Polarimeter at the VTT between1999 and 2012. These data were used to study a possible long-term decline of solar activity. The results on the study of the quiet photosphere have uncovered solar phenomena never reported before, namely, (1) the presence of horizontal vortical flows coupled to granular lanes. This vortical flows are of hydrodynamic origin given by the gradients in density and pressure of the gravitationally stratified solar surface. And (2), magnetic structures driven by supersonic flows whose origin shows signs of being coupled to magnetic reconnection processes taking place at small (sub-arcsecond) scales in the deep photosphere. The comparison of sunpot magnetic field and umbral intensity measured between 1999 and 2012 showed a dependence on these quantities on the solar cycle, but no significant long-term-trend that would point toward a grand minimum in the near future.

Publications

• Detection of Vortex Tubes in Solar Granulation from Observations with SUNRISE, in Hinode-4: unsolved problems and recent insights, L.R. Bellot Rubio, F. Reale, & M. Carlsson, ed., Astronomical Society of the Pacific Conference Series, 2011
  O. Steiner, M. Franz, N. Bello Gonzalez, et al, incl. W. Schmidt
  
• The formation of a penumbra as observed with the German VTT and SoHO/MDI, in IAU Symposium, D. Prasad Choudhary and K. G. Strassmeier, eds., vol. 273 of IAU Symposium, Aug. 2011, pp. 134–140
  R. Schlichenmaier, N. B. Gonzalez, and R. Rezaei
  
• Shear and vortex motions in a forming sunspot. Twist relaxation in magnetic flux ropes, A&A, 538 (2012), p. A62
  N. Bello Gonzalez, F. Kneer, and R. Schlichenmaier
  (See online at https://doi.org/10.1051/0004-6361/201118005)
• Supersonic Magnetic Flows in the Quiet Sun Observed with S UNRISE /IM A Xin Hinode-4: unsolved problems and recent insights, L.R. Bellot Rubio, F. Reale, & M. Carlsson, ed., Astronomical Society of the Pacific Conference Series, 2012
  J.M. Borrero, V. Mart´nez Pillet, R. Schlichenmaier, W. Schmidt, et al.
  
• The formation of sunspot penumbra. Magnetic field properties, A&A, 537 (2012), p. A19
  R. Rezaei, N. Bello Gonzalez, and R. Schlichenmaier
  (See online at https://doi.org/10.1051/0004-6361/201117485)
• Variation in sunspot properties between 1999 and 2011 as observed with the Tenerife Infrared Polarimeter, A&A, 541 (2012), p. A60
  R. Rezaei, C. Beck, and W. Schmidt
  (See online at https://doi.org/10.1051/0004-6361/201118635)