Narrow-band full Stokes polarimetry of small structures on the Sun with speckle methods
Institut für Astrophysik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany e-mail: [nazaret;kneer]@astro.physik.uni-goettingen.de
Accepted: 19 December 2007
Aims.For the detection and the study of small-scale magnetic fields on the Sun, it is important to obtain observations with both high spatial resolution and high polarimetric sensitivity.
Methods.A second narrow-band etalon and a full Stokes polarimeter, based on ferroelectric liquid crystals, were implemented in the two-dimensional “Göttingen” Fabry-Perot spectrometer/polarimeter at the Vacuum Tower Telescope, Observatorio del Teide/Tenerife. First observations with the Fe I 6173 Å line and their data analysis with speckle methods are described.
Results.The new polarimeter yields magnetograms of a field of view of 31″52″ with minimised seeing induced signals and without spurious signals as from the use of beam-splitting calcites. The achieved spatial and temporal resolution are 030-035 and 36 s, respectively. With a detection limit for the field strength of 16 G , a polarimetric sensitivity of 7-81015 Mx is obtained. Examples of intensity maps, Dopplergrams, and magnetograms from quiet and active regions on the Sun are discussed. Some of the results on solar magnetism are on 1) a pore with small-scale structure where we find a region with very low temperature gradient, 2) polar faculae with strong magnetic field signals and weaker signals in other areas surrounding them, and 3) small-scale inter-network magnetic fields with area fillings in the resolution elements of the order of 0.15.
Key words: Sun: magnetic fields / techniques: high angular resolution / techniques: polarimetric
© ESO, 2008